Xenon fast flashing green

I have just set up my Particle Mesh WiFi bundle. All went well but then, after 30 mins or so, the Xenons started fast flashing green. I have seen comments about Arris routers and IPv6 but, although I have a Virgin Media Superhub (rebranded Arris), there is no IPv6.

I set up the network again and, after 30 minutes or so, the Xenons started fast flashing green again.

Apart from the IPv6 issue, is this a known bug? Is there a fix?

I observed similar behavior when Device OS on the Argon in my mesh as well as the Xenons was updated to 1.2.1. I don’t know if there was a problem with different particles with different OS versions talking to one another or the multiple semi-simultaneous updates just causing communication problems.

My “solution” was many power off/on, reboots and flashing blink demo code until devices started talking to one another again.

Not much help. Hopefully a more experienced Particle user can chime in.

All are running 1.2.1. All devices are within 1m of each other.