Hi,
I think I found a bug in ArcGIS Pro when using 2 screen on the same computer. Some windows are disappearing when I try to move them. This bug only happen when I use ArcGIS Pro inside the secondary screen.
Step to reproduce:
- Use a dual screen setup (2 monitor on same computer). (I use windows 7 if that helps)
- Open ArcGIS Pro and place it completly inside the secondary monitor.
- Right-click any layer in the TOC and select "Properties".
- The property window will open in the middle of the map.
- Trying to move this window will make it go completly white.
Here is an exemple:

I am using ArcGIS Pro 2.2.0. I can't test with 2.4.2 (I don't have admin right on this computer so can't upgrade). Maybe the bug is already corrected in the last version?