This has been very informative. I am using mysql. This was an application that suddenly went "corrupt"... on my development.
I did some migrations, changed some relationships, the usual, and then bam! Won't update or edit this one entity. HOWEVER,
another clue emerged.. if I try to add a new record, it never completes the to-one relationship to Author.
I will remove all locks, rebuild, etc. and see what happens. Nonetheless, I do like just putting one lock in place on a version number.
Onwards with my other custom report project.
James