When you create a dialog on top of the vanilla map, the cursor starts flickering between the dialog mouse cursor and the tracking cursor normally used on the map. Performance goes down to about 10 FPS, scripts get executed very slowly and all ctrlCommits are very choppy.
When you switch to windowed mode (Alt-Enter) and move your mouse off the A3 screen, the flickering stops (Logically), but the performance immediately jumps up again and all animations are buttery smooth. Seems that the mouse cursor loop is the problem or maybe a vanilla MouseMoving / MouseHolding EHD. {F23949}