Illustrator crashes opening certain files + odd behaviour with text boxes

Hello.

Mac Studio 2022; Chip Apple M1 Max; Memory 64 GB; macOS Sequoia 15.6.1

AI 29.81.

I have two problems: 
1. When opening certain files, Illustrator crashes on startup. These files were created this year, they have a last modified date in january/february. I updated, tried GPU Performance both on and off, reset preferences, enabled content recovery with no avail.
I tried opening them on another machine and same behaviour. They worked for sure in February of this year.
UPDATE: I downgraded to 29.6 and now it works.
Maybe this needs to be addressed in v 29,61; 29,71; 29,8; 29,81 !

2. In some other files that actually do manage to open, text boxes seem blank (video attached).
They are there and full of text, if I copy and paste into new textboxes the text magically appears, but then sometimes it goes away again. From file preview (outside of AI) the text doesn't show.
It happened a few times before, but managed to fix simply restarting Illustrator. To fix it this time I had to paste all the contents in a new file. 
[the downgrade to 29.6 doesn't help]

Thanks a lot!