After doing some more testing, I've found out that it mainly happens when I use real DVDs and am not very close to my Mac. Thus, I suspect that Remote Buddy does not detect the button being released. When RB won't stop fast-forwarding, nothing can interrupt it, not even pressing the play button. So my guess would be that the "sticking" happens when the event of the button being released is lost. If a cleaner solution is not possible, it already would help if one could stop fast-forwarding with the play button.

Axel