Negative Play rate in an Anim Sequence added to a Montage Causes timeline to collapse

Adding animations with a negative play rate (playing backwards) or modifying existing animations in a montage to have a negative play rate causes the timeline in the montage to "squish" and is no longer functional.

Another separate, but related AnswerHub report: https://answers.unrealengine.com/questions/153035/461-anim-montage-cant-play-animation-backwards.html#comment-158989

Open a project that contains a montage and supporting anim sequences.
In the anim sequence change the play rate to -1.0
Open a montage that contains the anim sequence
Observe the anim sequence in the montage timeline.
The sequence will appear "squished"