Entities become unavailable

I have HA running continuously. It generally runs as expected, but quite often (after several days) certain entities become unavailable for no apparent reason, requiring a configuration restart to correct the situation. Most often it occurs with TP-Link KASA smart bulbs, but other entities as well.
Is this something that happens to other users, or is there a problem I need to resolve…any ideas welcome.

TP-Link Kasa is a known problem:

I also notice that the Kasa bulbs are still functioning through Alexa, even though unavailable through Home Assistant.