We have a hand held shower which slots into a circular holder that is attached to a pole that is attached the shower wall. The shower head slots into the circular piece a bit like a microphone does. The circular piece is screwed into the pole but tit slowly spins around under the weight of the shower head. I have tried to do the screw up tighter but after a day or so it comes loose again. Any suggestions?

I would contact the manufacturer. My dad had two defective MOen faucets and the company sent free replacements for both. This sounds like a design flaw. They may have something similar without this issue that you could swap out.

They make a thread sealant. Click on Thread Sealants | Buy Rivets | Rivet tools - Rivet Nuts & Other Specialty Fasteners to see. Good luck, Tom