acrobat dc has encountered an unknown error while signing

Dear community,

My adobe encounters a problem (like in the title) every time I try to add a signature to it. It doesn't crash, it just removes the signature.

Strangely, after 3 tries, and although the same dialog box opens, the signature stays on the document.

An other computer of mine is encountering the same problem. I tried uninstalling and reinstalling adobe acrobat without success.

what kind of information would you need to understand better my problem.

From my point of view there's something wrong with these pdfs I'm trying to sign, but I can't change them at all. Still, it used to work, and from what I read, it's kind of a rare issue.

greets