Just an update for those that are interested.
We swapped all of the APs it with the same model but the issue started again 2 months later. It seems as if the radios failed and caused them to reboot. Aerials were Meraki narrow patch antennas.
We then changed to MR46E APs and have been operating for months without issues.
As a precaution we had the site analysed for wireless interference with all of the APs turned off just in case something was overloading the radios of the APs. That came back all clear. We even ran the arena LED lighting at full power and they had no interference.
So, we are hoping that the chamber in AP model works fine.