I have ni on 400 episodes of Frasier Crane...yes we find them really funny when you consider what junk there is on TV.
I wanted to clear some memory but keep (lock) certain episodes so I selected one, then the Keep dialog, the screen went blank and when it revived itself ALL the episodes had padlocks.
So I thought if that happens then using Don't Keep it would remove all the locks but no it removed some but not all. I selected one of the padlocked episodes and repeated Don't Keep and it removed all the remaining padlocks.
Could this be the result of having too many episodes.