I just updated my 3 Cisco 150ax APs with new firmware 10.5.2.0. I loaded the firmware on the primary AP and it distributed the firmware to the other 2 units. It then rebooted them. For some reason it did not reboot the primary AP. So, I pulled the power on the primary AP one of the other APs became primary. And when the old primary AP came back it was not primary and the new primary AP loaded the new firmware on it and rebooted it. I am not sure I did everything right, but it all worked. I only had to load the firmware once to update all 3 APs.