Control Channel Problem

[TheLyppardMan]

I discovered this evening that if I switch on a 5GHz guest network, it messes up my control channel settings.

I have the 5GHz band locked to channel 36 because my Amazon Fire TV won't connect to it if the channel is in the 100's range. However, if I switch on a 5GHz guest network, the 5GHz band moves to the 100's zone. On the initial test, it moved to channel 116, so I repeated the exercise and it moved to channel 108. I checked and my Amazon Fire TV had lost the wi-fi connection. Note: the setting in the GUI was still showing channel 36 as the control channel.

I'm using the latest Merlin build on an RT-AC87U router.

 

[TheLyppardMan]

I've also noticed something else this morning. As well as changing the channel to 100+ when I switch on the 5GHz guest network, it also causes the isolation from the main network to be switched off. I tried this using a Windows 10 tablet which I use exclusively for monitoring images from a security camera. Using the 2.4GHz guest network, the tablet is isolated from the network, but if I switch on the 5GHz guest network, I can see and access all devices on my network.

 

[TheLyppardMan]

I tried this again a few days ago - I still had the channel-changing problem but I'm not sure whether the network non-isolation problem still occurred. Either way, I can't use it while this keeps happening. Is this a known bug in the firmware?