5GHz Guest Network Changes Channel

[TheLyppardMan]

I have just tried switching on a guest network on the 5GHz band, but instead of the 5GHz band staying on channel 44 as I have set, it changed to channel 136. Why would switching on a guest network mess with the channel settings? I need to have the 5GHz band locked to channels 44 or lower as my Amazon Fire TV won't recognise higher channels, so at the moment I can't use any of the 5GHz guest networks.