This ensure happens only when the Start and End of the sequence is set in the "neigborhood" of the keyframe and only if the project framerate is to be Fixed on 60FPS. If you for example play the whole sequence, setting the Start end End to values 0 and 6000 respectively everything works fine.
Results: When the level sequence reaches frame ~2270 the application throws an error
Expected: There should be no errors
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-72735 in the post.