BUG: Flipping between Keyframes stopped working on one specific layer

I use the Flipping panel to select which frames I want to flip.
I have several layers with both Keyframes and Breakdowns markers on some of the exposures.
All of a sudden flipping between only Keyframes stopped working on one of the layers. If I select also Breakdowns then it flips both between Keys and Breakdowns.
It works well on all other layers, I assume it’s some kind of a glitch. Have anyone experienced that?

Also if I mark some new exposures as Keyframes on this layer it works properly again. If I remove them again, it stops working.
After some time playing around with it I also realized that the Onion Skin on this layer also stopped working.
I have opened the scene in TB 17, and the Onion Skin works fine, but the flipping doesn’t…