The only way we have been able to get the system to change channels on the 5GHz radios is to turn on ChannelFly for a few minutes and turn it off. Otherwise every 5 GHz radio remains on the same channel. Runnin 22.214.171.124
126.96.36.199.101 has background scanning turned off on the 5GHz radio — see the release notes. You can still run 188.8.131.52.99 but support mentioned there is a risk of spontaneous reboots — which is why it's turned off.