@jeffrGGC - We've had similar problems at every event, though I am not knowingly running the UniFi AP manager software.
We also keep our PoE switch / injector in the shade, on a laptop cooler next to our main router - it normally feels cool as a cucumber. When possible we put the WAPs under a box stood on end so that it is open on one side for ventilation but shades the units.
When something takes AXti.me down it is usually the second database process that crashes. Sometimes I can restart just the second process window, but sometimes it requires a full restart of the machine to restabilize. Once that starts happening, I typically just unplug the WAPs from the PoE switch and that solves the problem - it means we can't broadcast live timing and results, though.
I really wish this part was more stable, and more easily diagnosable.
For next year I am strongly considering getting a cheap cellular hotspot for the main timing computer and doing away with serving our own live timing via wifi. But that offers its own disadvantages, such as the delay between uploads / refreshes - I really like having drivers and spectators be able to see timing and results in real time from their devices.
If I did go the cellular route, I would repurpose the WAPs as range extenders for the admin wifi, but I wonder if they will be any more stable under those conditions.
Brandywine Motorsport Club Autocross Chair
AXti.me user since 02 April 2015