Last shot, but... give it a try just in case.
Have you tried a full factory reset (of both units) and fresh reinstall of the OS with a computer?. This is not possible on the OG Homepod, but it is on the Mini.
"Reset HomePod mini with a Mac or PC:
Plug HomePod mini into your computer using the USB-C cable that came with it.
Wait a few seconds. If you're using a Mac, open a Finder window. If you're using a PC, open the latest version of iTunes.
Select your HomePod when it appears on your computer.
Click Restore HomePod".