I am using Win10 V20H2 (OS Build 19042.870) and WindowBlinds 10.86 (061 - Windows 10 Edition) - 64 bit OS right now. When I worked on the update of Sensua I was on Windowblinds 10.84 though and I also use Old New Explorer.
The Sensua skin worked perfectly in all cases, but I found what is causing these issues.
Any skin that uses UIS2 frames only has these issues without Old New Explorer installed, so I had no idea there even was an issue. If I apply any skin that uses UIS2 frames only I see these issues, so therefore this is a Stardock problem and not mine. Hope they can fix it.