It might be your packages or config. I use the WRT32X (same hardware as you) and have a 23 day uptime since flashing rc6, no stability issues. Running dhcp, firewall, adblock, samba, sqm cake, usb3 storage, etc. Completely stable. I'd say either wipe your config and try and or yea just stick with the stable build until 22.03 releases.
Here are the packages I install from SSH after a clean flash, just in case it helps:
I have run my wrt3200acm as a project work router network inside my operational network since before rc1 without problems.
Not specifically installed the rc6 but I have buildt from source around that time.
But not a single one of the 22.03 builds I have done has been so unstable that it reboots on that device. So I doubt the problem is directly connected with the 22.03 installed in wrt3200acm.
I would start by remake the configs from scratch to se if it helps (like you should always do when upgrading major releases).
Same problem with ZyXEL NBG6817 and 22.03 final. Did you solve the issue? Snapshot release seems having problems with pppoe restart so I will go back to 21.03.