Q Light Controller+

I can't seem to get video playback to work on Ubuntu. I just get a black window/screen. I've tried 2 machines, one running 16.04 one 18.04 and have QT5 and the multimedia plugins installed from apt. I've tried both the latest release (4.12.1) and the latest automated build version but neither work.

Is there a gotcha I am missing? Or am I best looking at a different distribution for running QLC+ with video in a reliable and stable way?

Thanks,