Hi Jcyxxx, I've experienced this 'issue' too. Chainik I guess seems correct, but I'm not sure about the IGP either. The 4712HQ Intel IGP [or something?] sometimes seems to give me issues too. 850M Laptop>4k, no madVR, not powerful enough. Not to drive from backseat but Billinear MPC-HC-Output resizer is a good suggestion. That helped me a little bit when messing with MPC and resizing to 4k fullscreen, or at least a larger than before windowed playback.
I've found that mpv and vlc through the purchased version of SVP are smoother for me because if those have resizers they are tamer than MPC-HC's.
I'm going to wait to upgrade to an 8k-240hz SVP-MadVR machine. With a 1950X and a future processor you'd probably have enough. Consider trying others players through the purchased license of SVP while it's still on Black Friday offer this year. Again, mpv seems to have fixed the 'resizer-IGP' problem (I'm supposing resizing somehow administrates through the 4712HQ IGP). If Chainik has specific feedback on IGP resizing or other known issues I would appreciate a heads-up here if that's alright. : )