Recurring slow leak/drip from shower head after plumber replaced cartridge and tried to fix the leak a couple of times

As indicated in the title, there is slow leak/drip from the shower that first started after the plumber replaced the shower (kohler) cartridge (and mixing valve). Since then, the plumber has come back and fixed the drip twice but the drip starts again after a few days of use of shower. Also worth noting is that every time the drip starts again, it is faster than last time.

The plumber has stopped responding and I may have to call another company now. Looking for advice on how to get the issue fixed or what to ask the plumber next time to fix so that it doesn’t come back.