Several of the BSAP-1840 are reported BG channel interference. Before chasing the air ways just wondering if there is an alternative troubleshooting.
Channel b/g/n (2.4 GHz) Auto
BG radio: non-802.11 interference detected - change the channel and then reboot the AP.
I would suggest upgrading to vWLAN version 2.6.2 on both the controller and APs. In vWLAN 2.4, this message could appear for many reasons, but it was not always non-802.11 interference. We have refined that code in a recent release and it should give you a better indication of whether these is an issue you will need to check into.
Please see our Upgrading BlueSocket vWLAN Controllers and Access Points guide for more information.