Signatures seemingly disappearing from signed PDF

[Jeffrey5D85]

Hello, I have an odd issue where users are reporting that digital signatures are disappearing from certain signed PDF files (seemingly at random).

We have a PDF form that we use for yearly performance evaluations, and we are getting a few reports where the manager will sign the document, then send it to the staff user for them to sign as well. The staff user sends the signed form back to the manager, the manager confirms the signature being on there, and the manager then saves the file on their Onedrive.

The manager then goes to reference the form days later, and they notice that the staff user's signature is missing from the document.

Note: I have been unable to replicate this issue so was wondering if anyone has run into this issue of signatures mysteriously falling off of a previously signed PDF form.

Thanks