Loossee goossee

What would be the best fix for the following at this point short of hammering out a few tiles,or cutting out a portion of wall on the other side to gain access:
My shower head water supply riser and tub spout nipple flap around like a very loose necked goose. Theory 1. Both the above are made of PVC or CPVC and are not fastened down to a block of wood or similar with some sort of strap. Theory 2. They are fastened down ,but because of there plastic type material they will always flap around when touched ,or when the shower head is adjusted.

The preferred way to install those is with a drop eared L screwed to blocking. Unless this is on an outside wall, it is usually easier to fix drywall than to repair pipe. You could try just filling in around the hole with some construction adhesive or silicon. Just give it long enough to set up well before using.

You should have an access panel behind the shower anyway. If you don't, you should create one. Once you do, you can fix the problem with straps or with shims.

Once the pipes are stabilized, you should caulk around your fixtures, including your tub spout. This will also keep everything from moving around.