Update x 2
I've reported this issue to Apple via Feedback Assistant.
Based on feedback throughout this thread I've been monitoring my HomePod's Mac assignment from my router and Home interface. I recently had to reboot one of my HomePods because it lost connection with the internet. Unplug for 5 seconds, plug back in. This was a near daily routine for my HomePod mini's paired in our bedroom. The original pair I have in our living room flawless.
I moved an IOT from Aqara that was near the problematic HomePod mini last week to 3 feet above the speaker an just to the left, avoiding it's line of sight to the router and its pair.
This improved the situation as HomeKit and our Shortcut routines became more reliable, going several days without a hitch. That is until this morning when the same problematic speaker disconnected.
I rebooted then checked my logs on the devices MAC address, as I have private IP set on the iPhone I used to setup the speakers up with, as previous replies suggested this feature could break things as it randomizes the devices MAC address to break tracking and improve security.
I have not changed this setting or reset my devices at this stage, I had previously completed a OS restore via Finder on my iMac, and as others have described changing this feature could wreak havoc elsewhere and I don't have time for that.
Today, following the reboot the MAC address remains the same, however my iPhone Home app says the speaker is "No Response" while my iMac HomeKit App says the speaker is "Paused."
Not sure what the issue is here, but it seems to suggest that my iPhone, connected to the same SSID is not seeing the status of this one HomePod for some reason.
I have long experienced issues with wifi devices on the same router with different active bands not finding other devices on the same network, either wired or wireless, if the other devices isn't on the same frequency it doesn't find it. This has been rare, but it's one of the reasons I avoid fencing my IOT devices off, it's complicated devices you don't want in that group to see what's happening in side it from outside the group.
I'm clearly not a network specialist, just an above average technical user.
I use a wifi 6 router from Amplify, it works well generally. I do not have its HomeKit router security enabled, as doing so limited the functionality of several temp triggers I need.
I'd continue to encourage people to reset their HomePods via USB, this provided some stability, then ensure there are no other radio frequency devices in between your problematic HomePod and your router. If you have a concrete or metal wall between your speakers and their router consider relocating the speakers for a short period to further identify possible disconnect causes. And if you live near a police station, fire station or other entity associated with secure or high powered radio frequency transmissions, you will continue to experience this instability when those devices are activated.
Don't forget to create a Feedback Ticket with apple and provide them with relevant use case details.
[Edited by Moderator]