The animations will blend together forming one animation and works fine until you undo and separate the animations that were put together. Causing animations to break.
p.s. Sorry for long video, 0:55 sec into the video you will see the undo happen and put both animation into one THICK PURPLE BAR.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-40682 in the post.