Quoting from https://github.com/openjdk/jfx/pull/82#issuecomment-575824678

Here are the steps I used:

1. Run TimelineTest2 (see the linked issue JDK-8210238)
2. Select cycle=2; Select AutoReverse
3. Play animation: it correctly goes forward from start to end and then backwards from end to start
4. Set rate=-1
5. Play animation: BUG? It still goes forward from start to end and then backwards from end to start
Subsequent calls to play do what I would expect, in that it goes backwards from end to start and then forward from start to end.
The same thing happens when switching back to rate=1 : the first time it continues the direction it was prior to changing the rate.