Water in Shower Won't Stop?!?!

Hey all, I'll keep this as brief as possible. Thank you in advance for all of your help!

We are getting a wet bar installed. The plumber created the new line and all. Then the next day, after one of our showers were used it would't completely turn off. Then the next day it did turn off. This evening, it just started on its own.

So what could have happened here. Could any of the plumbing work that was done have created this? In theory I can't understand how? All we did was add a line to the new wet bar. Could there be a rush of water pressure forcing it self through the valve??

Or is this a malfunctioning shower handle not turning off the valve? The coincidence would be big though.

Thanks again for your help.

sounds like construcion trash in the pipe got into your valve.

turn the water off, remove the cartridge and clean it...if it wont stop, replace cartridge

or orings..whatever you have