Sequential Pro One Pitch and Mod Wheels broken

A friend gave me a Pro One. It works and is in pretty good shape but the pitch wheel is broken in half and the mod wheel is split and heading for the same fate apparently due to over tightening of the allen screws. The mod wheel just spins around the shaft of the pot. You just can’t make it tight enough. I thought of filing a flat spot on the shaft to give the allen screw something to grab hold of and then I’d simply glue the wheels but I don’t want to do a hack job on a cool piece of vintage gear so I thought I’d ask if anyone dealt with something similar and could give me some insight on possibly a better way to handle it. Thanks!