In a way I'm glad I'm not alone! I have noticed that if I temporarily revert to playback through the primary device and then switch back to airplay to what ever the problem disappears! Recent updates have not changed the issue but, for me, it doesn't happen all the time.
It is such great shame that Apple does not produce a modern replacement for the AEX. It wouldn't even have to be a general router/print server. Just a good upgrade of the music features would suffice. The Belkin product recently announced (but mostly unavailable!) doesn't seem to be very good.
In the 21st century it should be possible to run a wireless audio system without having to wholly subscribe to one manufacturer's products i.e. Sonos, smart speakers etc. It's a reminder that companies produce what they want the customer to buy and use rather than what they actually want and need.