Bug in Airplay that it reverts to original setup name for Airplay speaker.
It is well documented in posts, from various community posts on several platforms, that there is an issue of the speaker name reverting to the original name when attempting to change it.
I have cleared all accessories with Airplay from HomeKit and tried to rename the Airplay speaker but, to no avail. The name reverts back to the original name. Surely someone at Apple understands why this is happening.
AirPort