Can't set play rate of media player to a negative value


I have a media player that plays some videos. I want to let the player control the play rate, so that he can fast forward or reverse the video.
But when I try to set the play rate to a negative number or a number greater than 3, the video just pauses.

Here are the infos:

I guess the media player just uses the Unthinned play rates. How do I use the thinned ones? I don’t really care if he is skipping frames.

Are you using buttons or a slider?

I’m just setting the play rate manually to -2.0 for now. But it doesn’t work