Hi guys, my first post so please go easy on me...

specs: 3 handle tub/shower faucet, don't know the brand, it's old (looking at least)

our upstairs shower is making this banging/machine-gun like sound everytime someone turns it on ever so slightly, but once it's turned all the way, the sound goes away too. not sure if it's the hot or cold valve (still have to check). it's the guest bath and it rarely gets used.

my questions are:

1.what is causing this?
2. is this something that can cause major damage to anything if not fixed ASAP?
3. can I just replace it with any other/different brand 3-handle faucet without ripping out the tiles

thanks in advance