Keyframes should disappear but they don't.

Hi everyone!

I was working just fine, but suddenly I had this problem.
If I want to draw a pose that will be on screen for just one frame, it doesn't disappear when it should. So all keyframes remain there on the screen, instead of disappearing to make the animation work.

PS. Onion Skin is not enabled. Don't know what happens.

Thanks in advance for any help!