HomePod mini designed to only work in a pair?

I have three HomePod minis - two paired and one solo. The pair works fine but the solo mini frequently drops sound. Anyone else having this problem with a solo mini? I’m starting to think the minis were only designed to be used in pairs.

Also, I’m on my second solo mini as the first one quit working after 5 months. The replacement appears to be a refurbished mini, but it is starting to show the same problems as the first one after just a couple of days.