stopping QMediaPlayer on i.MX6 hangs main thread

I have an Quick EGL application on i.MX6Q (Vivante drivers). The audio playback is moved to it's own thread. When I now play some audio and the audio stops because the playlist is finished I see a lot of frame drops (delay seems ~0.4s from rough measurements). When I run strace I see that the audio device is flushed and closed at this point, which seems to block the main thread.

I would like to get entirely rid of that cleanup for the moment, I only have one application and that will later reuse the QMediaPlayer and could benefit from the device still being open and ready. Even hackish things welcome, just give me a pointer where that unref happens.

The more general question is how to get the thing properly closed without blocking the UI…