Water stem replacement screwup

[RoyBarton]

I replaced my hot water shower stem two months ago. I don't know what's went wrong. A couple days ago I noticed the faceplate keeps unscrewing when I turn the water on, today I noticed it was leaking out of the back and into the ceiling.

The whole stem and everything is unscrewing, rather than just the knob turning. If I hold the faceplate in place and turn the handle, no leaks. Not sure what to do. Would putty on the back of the faceplate keep it from moving?

Thanks

 

[Breplum]

components need to be properly tightened. Gland nut specifically.