randomised
Occasional Visitor
my setup is very basic, it's just a home router with guest wifi enabled, no mesh, it's bridge mode to the DSL modemAs one of your steps have you tried doing the reset from within the GUI and checking off "initialize variables".
The other option is to do an "NVRAM Erase" from the CLI, then load the latest Asus or Merlin firmware, using recovery method and the restore tool if needed.
It certainly looks like you may have had some malware on that router at some point and factory reset isn't clearing all the leftover stuff, probably because it isn't using standard NVRAM variables.
I would start with just a very basic config after all the resets and see if any of the VLAN or wifi variables get recreated.
I've only ever had Merlin scripts on it
my feeling is the it's restoring from a nvram backup, where are they kept and how can I delete those?