Onscreen Video playback flicks.

whenever i am playing the project with Mp4 or Prores422 files, i find that there are random flicks of the video in the onscreen Window. As my computer is Imac 27inch late 2019 and running MacOs Mojave 10.14.6. and i am sure that the processing power of the Mac is powerful enough to just for playing back those files. How can i solve it? Does anyone encounter this problem before? Thanks.
( I have tried playing back those video files from the Preview video of the Mac or the Quicktime software, they do play smooth and soft).
Are there any bugs in the video playback in Nuendo10?

Hi there,
what you mean with flicks? I’ve also issues with Nuendo 10 video playback. I’m on a mac pro 2019, 16 cores with the base grafic card AMD Radeon Pro 580X 8 GB. I show you a two frames in which you can clearly see a horizontal cutting line (shoulder). Obviously not all the time but often my video playback is messed up by this random lines.
I’ve never get an answer from Steinberg.