I guess you have no problem with the riser you rather have a problem with the mouse
I have one mouse which does not work and when it does, the cursor jumps on the screen
I went to the store, I bought the cheapest one and it worked
So what would I advise you to even borrow from someone 2 3 mouses only for the test and then check how the amiga behaves
and how does the amiga behave without the mouse on?
And how does the amiga behave with keyboard on it
I use ARM like this