When I pulled the handle and escutcheon off and diddled with the shutoffs that are built into the valve, the cold water side was leaking a little. And some black rubbery bits came out of the spout when I turned the water on. Looks like the stops are failing and need to be replaced. Figured that out thanks to a commenter on Amazon who was trying to find the right replacement parts for his pipe thumping problem.

I have all the documentation from the original install, including the parts diagram with replacement part numbers for the various components. A lot of the part numbers changed after Danze was acquired by Gerber some years ago. I couldn't find a direct match for the Check Valve Set in question when I did my own searches, and Claude and DuckDuckGo's AI bots tried to help but I wasn't confident they were giving me accurate part numbers so I could order something.

I called Gerber this morning and a very nice CS lady (not AI) listened to my story, asked a few questions, and processed an order to send me replacement stops under warranty. Gerber didn't even require a copy of the original purchase receipt (which I have). Took less than 10 minutes and I'm pretty sure I'll get the parts I need. She said 5 to 7 days for the order to get here.

Now off to look for out not-too-frequently-used metric socket set I'll need next week to get the old leaky stops replaced and the new ones in...