18.104.22.168 auto-updated, stable so far
I have one RBR50 and originally had one RBS50. I added another RBS50 to give my Ring security cameras better access, and one of them was running 22.214.171.124. Oddly this seems to have triggered an update across the board to 126.96.36.199. After reading all the threads here I was worried.
It's been up for 4 days without a crash or reboot, and I am getting ~300Mbps throughout the house, about the same as before. If it stays stable I may try enabling Circle but as of yet I haven't wanted to add risk.
I did have an odd experience. My son had an older Netgear in the basement, and it was giving out DHCP IP addresses on Ethernet, and was having a very negative effect on the Orbi's performance. I've turned it off for now, but it was fine with my old firmware.