IIRC, you are supposed to run at or under 125% on 4K. But I never tried other than 100%. Maybe try that.
Is your view by any chance controlled by a template and you accidentally tried to edit the visibility overrides in the Graphics properties? if so, edit the template or use temporary view properties.
I have to say, this year the new version had no "have to have" features for me and is the first year I didn't convert my current projects right away. And this also is the first year where there seem to be so many problems. I opened a sample project right now to look this up for you. When moving the properties pane, it took some seconds for the properties pane to render properly. Maybe this new version doesn't like my ancient quattro P 2000, but that never happened before and we are just talking moving the properties pane. This year may be the year i don't upgrade my projects before the service pack is out.

Revit Version: R2026.2
Hardware: i9 14900K, 64GB, Nvidia RTX 2000 Ada 16GB
Add-ins: ElumTools; Ripple-HVAC; ElectroBIM; Qbitec