MultiLanguage Textarea not persisting after upgrade

[Floioioi]

I upgraded ProcessWire from 3.0.39 to 3.0.210 and recently to 3.0.229. Now when I save a page some MultiLanguage Textarea fields are not persisted in the DB, the page is saved but the field value does not change.

I checked out the data with before and after save hooks, and there I can see that the field value is correct before save and after saving it reverts back to the old value.

Does anyone have an idea how this happens or how I can debug this better?

[Floioioi]

After some more debugging, I have new information which frankly makes this even more frustrating.

After upgrading to 3.0.210 I also added a new "Repeater" field and added it to a template. Now all the fields after this Repeater cannot be saved, still no error message. I moved the repeater field to the last position in the template and now everything can be saved. I'm still mostly looking for a way to debug this properly.

I also increased the values for max_input_vars but that does not have any effect.