There was no documentation when setting up a R6250 in AP mode about why the guest mode defaults to "Allow guests to see each other and access my local network" AND it's greyed out and checked which means I can not change it.
If I take the router out of AP mode then I can uncheck the box but that's not really an option in my current setup. Also if I uncheck the box & then go back into AP mode it goes back to the greyed out and checked box.
When used as a AP guest cannot be isolated therefore it's greyed out. To do what you want it would require VLAN which the home products do not offer is my understanding.
Router do have small VLAN when used as router mode. Problem is when AP mode is used, VLAN that was tag with internet port no longer works so it breaks the guest usage.
