I had the problem that there was a Thread network from previous experiments and HA always complained that it couldn’t communicate with that network (I already had it deleted a while ago).
I think I saw a discussion that it’s a known issue that there is no way to chose a network if there are more than one. It was mentioned it’s being worked on.
I had to play around a bit to ensure Devices & Services > Thread > CONFIGURE
only showed one network “Preferred network” “home-assistant” with “1 border router” to not get any related errors.
Perhaps mDNS is slow to drop such collected information (I have no knowledge about how that actually works)
How to configure preferred Thread network has some discussion about that