JSON error popup with Lithuanian language after 3.10 update

Hi ,

I'm not the greatest BUG submitter in terms of providing with all possible information, however , looking at one reply in fomum (https://moodle.org/mod/forum/discuss.php?d=415257#p1673743 ) I understand that this bug affected not only my installation , thus it should be checked somehow.

More and more teachers complain about this, and i cant understand where i can fix this.

The problem - we where absolutely fine on 3.8 without ANY TROUBLES , and after we updated to 3.10 + (currently (Build: 20201204)) popup with SyntaxError: Unexpected end of JSON input after 3.10 update started popping out for many teachers and pupils . (see screenshots of bug and console in forum) .

However, i found out this ONLY POPS out when Lithuanian language is selected , plus most often this would happen if there is video attached anywhere on a page or subsection (but this is not required, i just atached screenshot of bug happened on marking page without video).

Please try to help me , contact me if you need any access for testing on out live system, as we would appreciate this is fixed soon.

PS- attached screenshots for forum here