Hello, I also have an OLED TV, and I haven't had any issues with the MyTVOnline 4 app. It plays everything with good quality both audio and video. It actually performs even better than the MyTVOnline 3 app. I haven't encountered any problems.
It might be the settings in the MyTVOnline app, such as AFR for live TV and VOD/series. You could try toggling them on or off.
Thanks for the reply yes as said I spent quite a while doing all manner of settings, recommended for the tv and box with other posts about this issue somethin about delacing 25fps 1080 even went into developer mode (obviously shouldn't have to do this) but nothing worked for me until I gave up and installed tivi and that seems to be smooth.
So fingers crossed for MOL4 as would like to use the app that I paid for.