language file gets corrupt

Hi everyone
I hope this is the correct forum. If not I ask kindly the moderator to move it to the appropriate place.
I have a problem with translations of one plugin. The translation files get corrupted at different times. (I have multiple sites on the same server – same theme, same plugins, different domains and different languages that work ok).

I removed all non essental plugins (All in one security plugin, W3 cache,…). I even searched through the DB is anything was left by some plugin..
I uninstalled my plugin (cookie notice) and set it up again. The plugin translations work.

So what happens?
Something triggers a copy. At different times during the day so I guess some request? The translation files get copied into /wp-content/languages/plugins folder and the translation no longer works. I looked at the po/mo files and the only difference I could find is that the .mo file increases from 3KB to 10KB. Poedit doesn’t report any error on these files.
If I overwrite the files in the /wp-content/languages/plugins folder the translations work again. Until a rewrite is triggered and the files get corrupt again.
I tried changing the permissions to read only (400) but that doesn’t work as it reverts to 700 (I have only FTP access). I tried deleting the folder but it gets written again together with all the translation files including the corrupt ones from my plugin.
I searched through the plugin and the functions.php but I could not find what could be making this overwrites. I never experienced anything like this from any other WP sites.
The last idea I have is to ask the server administrator to “put a lock” on these two files. But I would really prefer to find out what is happening.
Has anyone experienced anything like this before? Does WP include some procedure/function that could be doing this write/overwrite? If so is there a hook I can use to stop this action?

BR, Igor Bagon

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