Not sure this is the correct place to report an error/bug in this latest firmware, but since updating to this, my secondary router, which runs as a media bridge, now gives me a browser flood each time i click the wireless network name at the top of the main page (takes you to wireless general page), and try to use the drop down box to select 5Ghz.. soon as i do that, the browser will reload itself every 0.5 seconds, so I can't actually set it via the interface at all. Tried a few different browsers, and even from my iphone.. same effect.
My primary router, which is running in router mode has no such issues.
Both are RT-AC87u's.
Also, whilst I did get the bridge to work over 5ghz anyway, by using the wizard, and manually entering the ssid / pass, it is really unstable for gaming. Might get 5 mins or an hour, but seem to get a lot of disconnects going over the bridge with my PC. It was far more stable on the previous 380.65_4 that i was using (edit. I should add, the routers are literally about maybe 8 meters apart, with a single wall, between them. A meter or so to the left and they'd be looking at each other through a window even - so distance shouldn't be an issue). Last thing is, changing ANYTHING (even on the 2.4ghz radio) on the media bridge router, results in the bridge (5ghz) disconnecting - even if a 'soft' save, that normally isn't rebooting the router at all (see the progress going 20/40/60/80/100%). This in itself wouldn't be an issue, except that it does not reconnect at all without rebooting the router, or going through the setup wizard again, and there is no simple 'connect' button. Rebooting the router does make it reconnect after a time.
2.4ghz seems fine on the main router.