Belkin RT3200/Linksys E8450 WiFi AX discussion

Hey all,
Picked up a couple Linksys E8450s on sale with the intention of installing OpenWRT and using them in "dumb" AP mode, eventually in 802.11s mesh mode. Tested with the factory-compatible snapshot, and things worked very well for a few days.
Went ahead and did the UBI install from the prebuilt images on github, but saw the same problems with the network quitting that a couple of people seem to have mentioned above. Installed the latest snapshot via Attended Sysupgrade yesterday to see if that would help, and it did. BUT...
It randomized the ethernet macs and, not realizing this, I thought I had locked myself out. Ended up doing a full reset before figuring out what it had done. Is that normal? I generally set up my DHCP server configured so MAC addresses get "static" IPs. This is very useful after a factory reset on APs, switches, etc.
The sysupgrade also re-activated odhcpd and possibly the firewall, which I had disabled, and I am wondering what the proper OpenWRT way is to avoid this when doing a sysupgrade. Or is the proper upgrade procedure to backup, sysupgrade, reset to defaults, and restore? I'd like to be able to upgrade devices in-place, especially with the one probably going in the attic.
Many thanks to all the devs.