Ok, thanks for the video!
I hadn't realized you run rpix86 within the X environment. Can you check whether the mouse works when running from the console shell prompt? I believe those two run environments have different mouse emulation, so it is possible that the mouse works better when running rpix86 from the shell prompt.
Running from the shell prompt makes rpix86 run almost 2x faster, so it would be the recommended environment in any case.