I am using assignment annotation feature (with Google Drive file conversion) for adding notes to files that students are sending to me.

Since some time I'm unable to open and annotate PDF files. (same with doc files) I'm getting "undefined" error, see screenshot below. HTTP 500 error is returned for mod/assign/feedback/editpdf/ajax.pdf request.
I enabled extra debug messages, but no additional information is provided.
However, jpg files are correctly converted to PDF and I am able to see them.

My Moodle version is: Moodle 3.11.4 (Build: 20211108)

My Google drive file conversion is configured correctly: