drips

My master shower dribbles and drips when the guest bath/shower is used. Both the valve and cartridge(Single Lever) have been replaced and it's still doing it. What the heck?

Hello. I have a new Kohler Wellworth I'm about to install. I got it online and had to get the tank redelivered because the first came in probably 100 pieces. Given that distraction, I carefully inspected the bowl upon delivery and deemed it perfectly acceptable. Now that I'm preparing for the...