[workaround for always fast flashing green found for me]
I found an old Dlink DIR 505 “All In One Mobile Companion” (with modes as router, hotspot, etc.)
I put it in Router mode between by Linksys WRT1900AC and the argon gateway
and the xenon’s have all been breathing cyan ever since.
If it was just an ip6 thing then I am not sure why just disabling ip6 on my main Linksys WRT1900AC didn’t work.
====EDIT====
I SWITCHED TO A DIFFERENT WORKAROUND
I DELETED MY 3 DNS ENTRIES DOWN TO 2 DNS ENTRIES AND DISABLED IP6 AND MY WRT1900AC IS NOW WORKING WITH THE ARGON/XENON MESH)
SO THAT MAY BE AN OPTION FOR THOSE HAVING THE ARGON/XENON ROUTER ALLERGY AND WITHOUT AN ALTERNATE ROUTER
===END EDIT===