Unisntalling serves the purpose of checking if KAV actually disables itself properly.
Several AV tools do not and still cause slowdowns even when disabled, as I said. There's only one way to find out if that is the case. If it isn't, install it again and we can move on. But if it is, and we don't test it, then we will never get to the answer as we're intentionally avoiding testing a possible answer.
How to find components causing high CPU usage has instructions on how to find out which component is using the CPU within the dopus.exe process. That may point in the direction of a particular driver or DLL.
However, it the CPU usage is not high for the duration of the slowdown, then this is probably not worth trying.
Try turning off everything under Preferences / Folder Tree / Contents to minimise what's shown in the tree. Does that make any difference?
Also, try turning off Preferences / Folder Tree / Options / Automatically expand to current folder.
If you hover over the spinning circle, what does it say?
That circle usually means the file display is being populated. Which columns are shown in the file display?
Does the spinning circle show even in the empty folder?