Bug with Guest Network?

[JeremyGNJ]

I have this problem with my RT-AC86U:

1. Everything works fine with my standard WiFi SSID
2. I enable guest network, (WPA2, and access to Intranet DISABLED)
3. Guess Wifi works, and cannot see Intranet devices
   
4. HOWEVER...then all of the sudden none of my Wireless devices on the standard SSID can talk to each other. Wired devices can communicate with WiFi devices as expected.

It's almost like turning on the guest network enforces isolation for all WiFi devices. I found a few links online of other people having this problem.

One person said if you go into your normal Wifi --> Professional, then toggle AirTime Fairness off and back on again it fixes the issue. This actually WORKS for me, but eventually just breaks again.

Is this a known issue? if so, does the Merlin firmware address it?