I've been having periodic issues with people trying to electronically sign PDFs. Saving the document to a server, having the signatories open it (one person at a time!) and then trying to sign and then getting an error message "The document could not be signed". This corrupts the file in terms of signatures; once that error appears, nobody else can sign any other signature space, they get the same error message, and signatures are deemed "invalid".
Has anyone else experienced this issue, and if so, what are the possible solutions?