OG Homepod Stuck in Loop and Can’t Reset

I have three first generation HomePods which were all working perfectly until yesterday. Now, one of them appears to be stuck in a boot loop.

Yesterday afternoon it stopped responding to voice commands and the multi-coloured led was circling for ages, and it was not touch responsive. I left it for a bit, came back, and when I touched the top again I noticed the white spinning display, followed by a volume controls flash every 10 seconds or so.

I tried unplugging it, and it powers up, the white spinning lights come on, then after about 10 seconds, the volume controls flash, a second or so later the white spinning lights go out, and it (appears) to restart over and over. If you hold your finger on the control panel to reset, it turns red, but then the volume controls flash and it’s back around the loop.

All three were running v18.2 and the logs of the two working HomePods appear to have had an OTA update last night in the small hours of the morning. I’m wondering if this is something to do with it?

Previously, no issues, no cracking, pops, etc. it’s worked perfectly.

I’ve read elsewhere this sequence can seem terminal, but where I’ve seen videos attached, the Volume flash appears much faster than on mine so I’m hoping it might not be quite the same issue (false hope probably)!

Any suggestions are most welcome.