The problem isn't the shifter, I was just explaining that it is like a friction shifter so that's how I can reverse the chain shifting off the ring incrementally. Without touching the shifter, if I ride a mile or so the chain will visibly move left (sometimes right) of the big cog on my triple front. I can stop it by decrementing or incrementing the shifter slightly. What I don't understand is what could make the chain move out of line on its own? I pulled on the cranks and they are tight, and this wasn't happening before the mechanic reinstalled the rear hub motor wheel.