When I run either "git annex add" or "git annex status" on a repository with PDF files, I'm getting the following errors:

Syntax Warning: May not be a PDF file (continuing anyway)
Syntax Error: Couldn't read xref table
Syntax Warning: PDF file is damaged - attempting to reconstruct xref table...
Syntax Error: Couldn't find trailer dictionary
Syntax Error: Couldn't read xref table

I checked the PDFs and I can open them.

What is triggerring these errors? Frequently these errors freezes the git-annex process and I have no choice but to kill one by one all the spawned git processes.

Again, I'm in Windows 7, using Git 2.28.0.windows.1 and git-annex 8.20200815-g335aae266 on a newly-created repository in an NTFS partition.