RT-AC56U Repeater kills RT-AC56U Parent Routing

[Chinquapin]

I have two RT-AC-56U routers, both running the same version (380.61) of Asuswrt-Merlin. I set up one as a repeater using several different configurations, starting with the suggested defaults, and then using different SSIDs for the repeater to see if that helped. I reset the repeater to defaults a few times and started over. In each case, the repeater works fine, but the parent router goes wonky every time. It stops routing WiFi-connected devices for no clear reason, even while the repeater-connected devices are fine. Wired connection to the parent router isn't affected (my Ooma voip device). If I power-off the repeater router, the parent router returns to normal. That's about as simple as I can make it w/o providing lots more and likely extraneous detail. Parent router is downstairs, repeater is upstairs. I've placed the repeater in the same room as the parent router just to make re-configuration more convenient, but it's off now as it kills the parent router's connected devices' internet connection. WiFi connections aren't broken, they just don't route with the repeater powered on. Not at all sure this is a Asuswrt-Merlin problem, but since that's what I'm running, I'll start here. Haven't reverted to the Asus firmware, though perhaps that might be a next step unless other suggestions are offered. Many thanks.

 

[Snoopotic]

Check twice that your asus in repeater mode has dhcp disabled or is running in another subnet.

 

[Chinquapin]

I recall that both of those were default settings when using the configuration wizard. And I recall noting that DHCP was disabled on the repeater, and I also manually changed to a different subnet out of caution.

BUT, there's a weird intersection between the two routers. EXAMPLE: if, while on a WiFi connection to the parent router, I log into the parent router's web interface, it often but not always shows the REPEATER interface, as if I'd logged into the latter. Sometimes logging out and/or closing/reopening my browser takes me to the parent router. Weird.