No problem today. Probably user error...

There was one problem though: the very last frame didn't fit anymore after "auto (keyframes)". Or rather, the second to last (not a keyframe) was adjusted as if there was nothing to come, even though there was one more frame (keyframe).
I simply ended up synching everything from the second to last to the last frame.

Anything I might have done wrong? Don't see it at the moment.