I've had a look at the documentation and it states:
An exception to this daily update is an automatic channel change due to a radar detection event or high noise interference. If an AP detects a radar event on its current operating channel, that AP automatically changes to another supported channel to avoid radar interference, and does not wait for the daily RF configuration update from the Mobility Master. An AP may also automatically change channels if a very high noise level is detected on the current channel, if at least one other channel is free of noise.