silicon , fixes everything ........... ask any plumber ....... thatel be $60 x 4 minimum fee thanks

Pretty common occurance.
I recently shortened an adjustable paddle recently by removing the clamp, cutting to desired length, and carefully sawing a new slot. The clamp came loose without too much force by inserting a screwdriver into the gap and twisting gently. I had the same problem with slippage, so I removed the clamp and inserted a shim consisting of a piece of flexible plastic which was approximately the thickness of a business card between the paddle shaft and the clamp. I used a piece of paper to provide a template for the plastic. It took a few trial and error cuts to get the paper template to just fit inside the clamp and not stick out, top or bottom, or foul the slot. then I used the template to cut out the piece of plastic, sprayed both sides with spray adhesive and inserted the shim inside the clamp between the paddle and clamp. If one piece of plastic did not do the trick, I was going to add another or look for a thicker shim material, but so far so good!
Sorry for the wordy response, but it was a pretty clean and easy fix.

duct tape