ok that did help a little at least to give you a pointer in a certain direction.
In your logs I frequently see this:
org.xml.sax.SAXParseException; lineNumber: 2; columnNumber: 1; Content is not allowed in prolog.
There has been a topic in the past where the result seems to have been that the workflow somehow got corrupted - can you try and follow through with what happened after this response from Scott? It sounds like you can open one of the .xml files to see if it got corrputed (if you see structured stuff … then you should be good - if you see random letters and numbers - sort of gibberish… then it might have gotten corrupted in which case I am not sure if it can be reversed…)