Handwritten notes disappearing in the Notes app

I use my iPad Air 2024 and Pencil Pro to take notes for college using Apple's Notes app. Recently (over the last month or so) my notes have been disappearing.

So my notes look like this - I handwrite the date and subject, then I type my tags on the keyboard and under that I write the notes.

When I close and reopen the app, everything is fine, but a few days later, the last part, with the actual notes, disappears. Interesting thing is, that only happens to one subject and only on practice lessons. Could the tag combination be the problem (which it wasn't for the whole last semester)?

And please, no "update and restart the device" answers, done that.