Inexplicable fault out of the blue.

Hi everyone,
All of a sudden my script has been throwing an error, for which it tells me to llok into "logs/errors.log".
The error seems to affect my admin part only, the first symptom is a notice on the bottom that no data can be found in the database, yet my items display on the shop part.
Then I get the error message in various parts of the settings, eg. email.

Looking at the log file shows me the following:

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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:49AM]
[Error on line 91 in file /home/mvmotk/public_html/shopnl/admin/templates/email.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:49AM]
[Error on line 137 in file /home/mvmotk/public_html/shopnl/admin/templates/email.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:49AM]
[Error on line 24 in file /home/mvmotk/public_html/shopnl/admin/templates/email.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:49AM]
[Error on line 26 in file /home/mvmotk/public_html/shopnl/admin/templates/email.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:49AM]
[Error on line 27 in file /home/mvmotk/public_html/shopnl/admin/templates/email.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:49AM]
[Error on line 91 in file /home/mvmotk/public_html/shopnl/admin/templates/email.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:49AM]
[Error on line 137 in file /home/mvmotk/public_html/shopnl/admin/templates/email.php]
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[Error Code: 8] Undefined variable: lng_1_2_admin
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 35 in file /home/mvmotk/public_html/shopnl/admin/templates/dashboard.php]
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[Error Code: 8] Undefined variable: lng_1_2_admin
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 47 in file /home/mvmotk/public_html/shopnl/admin/templates/dashboard.php]
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[Error Code: 8] Undefined variable: lng_1_2_admin
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 59 in file /home/mvmotk/public_html/shopnl/admin/templates/dashboard.php]
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[Error Code: 8] Undefined variable: lng_1_2_admin
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 35 in file /home/mvmotk/public_html/shopnl/admin/templates/dashboard.php]
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[Error Code: 8] Undefined variable: lng_1_2_admin
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 47 in file /home/mvmotk/public_html/shopnl/admin/templates/dashboard.php]
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[Error Code: 8] Undefined variable: lng_1_2_admin
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 59 in file /home/mvmotk/public_html/shopnl/admin/templates/dashboard.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 14 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 19 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 20 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 21 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 265 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 339 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 382 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 391 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 406 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 410 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 425 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 429 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 433 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 437 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 441 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 445 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 454 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 14 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 19 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 20 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 21 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 265 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 339 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 382 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 391 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 406 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_settings
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 410 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 425 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 429 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 433 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 437 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 441 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 445 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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[Error Code: 8] Undefined variable: lng_1_2_sett_aff
[Date/Time: 31 January 2020 @ 01:55AM]
[Error on line 454 in file /home/mvmotk/public_html/shopnl/admin/templates/settings.php]
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There are quite a few more of these, but they all seem to concern the same file.
Does that ring any bells?
The error messages have even taken over some of the fields in the settings windows.
Any help will be very much appreciated.
Frankie.