Cannot Load notes/file corruption

[megaobanana]

Describe the bug

I imported a pdf (20pages, with only images) as note background and used stylus pen to take notes.
All of the functions are working as expected at first.
But after I took notes for like 10 pages, things started to go weird.
I saved the note on exit, but on the next time I reopened the note, pdf background started to go missing after page 10. I saved again, and then reopened the note, then all things were gone. A banner popped on the top saying "Read-only mode. cannot load the note. It may be corrupted or being downloaded"

To reproduce

import a pdf background of 20 pages
take notes for like 10 pages, then save, reopen, then save, then reopen

Expected behavior

not having file corruption

Saber version

1.33.1

Device

• Device: XiaomiPad 5
• OS: android 12

Anything else?

No response

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• I have searched for similar issues (both open and closed) and cannot find a duplicate
• This is not an automated submission and has been written by a human.