It may be that you are hitting the problem that it is careless with deleting temp files. If so a workaround is to move aside the two Fritzing temp directories
AppData\Roaming\Fritzing* and
My Documents\Fritzing*
and start with a clean slate. I often do this when making parts as an error will often get remembered (and thus repeated) until I clear the temp directories. I usually do both to clear everything but you may only need to do one or the other.