There is a 5ghz radio profile and under that is an ARM profile. Did you assign the 5ghz radio profile to channel 36 and set the ARM profile under it to disabled? In addition, in the radio profile, you would need to set the channel width (20). In the ap-group, the Regulatory domain profile also needs to have channel 36 enabled to be able to set the channel correctly. Do you have a screenshot of your settings?