Digital signature field can't be signed

I have a fillable PDF we have been using for years, never a problem with the digital signatures until twice now this last week.  I know, you're not supposed to have multiple digital signatures, but that's how my work wants it and I can't change that.  Anyways, twice now the last required digital signature field that the manager signs has been getting a message saying 'This document can't be signed'.  The form has to be filled out again and all digital signatures are filled in and the manager can sign no problem.  All the other 20 of the same forms each day have been working fine as usual and the manager has been able to sign just fine.  The only difference I can see between the one that didn't work in Figure 1 and the one that works in Figure 2 is the order of Revisions are not in order, even though the time stamps say they are.  On Figure 1 Rev 1 is showing as Mike but it should be Alexander as he signed first, but he's showing up as Rev 4.  What could cause the revisions go out of order when signing?  The employee fills it out, signs it, emails it to the Foreman to review and sign, sends to the Foreman 2 to sign, the timekeeper signs, then the Manager signs.  Yes, it's overkill, but I can't do anything about that.  Anyways, the Manager's digital signature field is set to lock when signing and Figure 3 are the names of the digital fields in the original document.  Any help would be appreciated.  I can't find anything on the forums on this issue.