The right (rear) shifter on my road bike slips down after I ride it for a while. The last time this happened I unwrapped the tape moved it back into place, and tightened the screw hoping it wouldn't happen again. But it did. This hasn't happened to my left (front) shifter yet, but I would like to avoid that because when it happens during a ride it rotates my wrist forward which makes my hand fall asleep. Not to mention it is extremely uncomfortable. Is this only happening because I tightened the wrong screw, or didn't tighten it enough? Or possibly because I'm right handed and favor that side with more of my weight, which pushes it down faster? If there's any way to fix this myself that would be great, but if my LBS is the best bet for the fix that's fine too. Please help.
Thanks