Hi Mia. Thanks for attaching the error log. It contains very useful information to debug this issue.
I am afraid that in this case, we can't blame your contributed plugins. There was a bug in the language customization tool itself - MDL-26348. The bug affected Oracle databases only and your site is apparently running at Oracle database. That bug was fixed in Moodle 2.3.2. Please upgrade your Moodle to the most recent 2.3.x version to get rid of this issue.
Languages
Language customization - error reading from database
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