Jup, I’m back, sorry for the delayed answer.
The short answer is, this is not a bug, but a limitation that has no proper workaround, so it will stay as is for the foreseeable future.
Here’s the longer answer to explain the technical aspect of the problem:
The weird thing here is that you only observe this with XP11 running.
Normally when you set the DPI to higher values, you always will have that effect.
As you can see, UI elements like headers, textboxes, dropdowns, etc, will sort of break, when you change DPI.
That’s not a bug, but a a combination of limitations of the UI technology CLS2Sim is currently built upon and its design.
It was optimized from start to run on XP, which was never intended for high resolutions.
(It uses Winforms instead of WPF, with a fixed size UI.)
This isn’t possible to fix, except for starting from scratch, so for the foreseeable future it will have to stay that way.