A user needed to edit a record but was getting a message that the record was locked. I did a forceunlockallrecords in that database, but the user continued to receive the locked record message. I connected to her computer and saw it happen, but did not know what to do other than I copied and pasted the record and deleted the first one. That fixed the problem.
You could add this to the pile of strange things that have happened for reasons still unknown. Sorry I don’t have more detail about what she did before the problem began.