Total Commander

When compare contents window is first displayed, the mouse wheel scrolls the panel text as expected. However if focus is lost - for example by clicking on the button area at the top - and then the panel scroll bar is clicked anywhere, the mouse wheel does not scroll the panel text. I have to click on the panel text to enable mouse scrolling again. Unfortunately, clicking the panel text resets any selected text.

I can confirm that - you need to click on one of the lists to give it back the focus. I don't think that it can be avoided.