This was able to be reproduced 100%. I encountered this during a Regression pass. I was trying to give myself more working space and remembered that hitting "Home" focused the space in sequencer, so I thought I would be able to do the same thing here, but I think since there is no real end in the UMG timeline, the home goes on forever and crashes to editor.
Note Tested in 4.13 and the crash is present. This is NOT a regression.
Result: The editor freezes up and crashes
Expected: I am able to focus the timeline by pressing home and then be able to scrub the timeline using RMB
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-37412 in the post.