This is strange to say the least - OCCT doesn't do much to your GPU with its GUI, just regular WPF stuff.
Can you give a shot to HwInfo's latest beta ? https://www.hwinfo.com/forum/threads/hwinfo-v7-01-4425-beta-released.7206/
Also, do you have any other monitoring program running ? I'm thinking of Corsair commander Pro, Asus AI Suite, Corsair iCue, ... They are known to cause issues.
A final check is to check if you have RTSS (RivaTuner statistics server) installed. This hooks into every known 3D app, and has caused issues in the past (because if it has a bug, it may cause other app to crashes - happened in the past).
Also, what's your GPU + driver version ?
Did you try a reboot ?
I'm fishing for stuff blindly here, I am sorry to ask you so many questions, but I fail to see what would cause that issue...
(replying to myself)
After spending two hours on this, my conclusion is that there's very little I can do. Most of it seems related to WPF technology. As soon as I start adding controls, the resize gets laggy, the larger the window, the longer the resize is.
The best "result" I could get is to delay updating the window content's resize until you let go of the drag. It's not final, but here's a preview. Makes things feel "faster" at the cost of the preview : https://www.ocbase.com/misc/resize.delay2.gif
What are your initial thoughts seeing this ? :)
An error detected means you have something wrong with your setup. It's like OCCT asked your computer for 2+2, and got 5 as a result. I'd suggest you go read my FAQ : https://www.ocbase.com/#_faq - there's an explanation of what an error detected means in the "