The first question that comes to my mind is; is this the only document that has a problem? Try saving a copy as an .odt file and see if the problem persists.
I have never used Unstable, so I can only throw out guesses. Perhaps it is one of those Unstable bugs that lasts for a day or two? A problem with an LO update? .doc files do not like your personality?
Someone who uses Unstable might have some insight.