I have an AX1200i that I bought new off Newegg a few weeks ago. I am disappointed that it didn't have the USB dongle in the box or the connector cable to hook up to iCue. That was one of the primary reasons I bought the PSU. But, that is a separate topic.
This new PSU kept randomly powering off. Sometimes it'd go 6 hours. Sometimes 15 minutes.
I have the PSU mounted in a Corsair Obsidian 1000d with 13 case fans.
After a week of troubleshooting, I found the root cause.
The Obsidian 1000d has an an exhaust vent at the bottom of the case where you mount the PSU. The AX1200i manual says to mount the PSU fan so it is facing the vent (down). That is a mistake.
Heat travels up. So, the bottom side of the PSU (facing up), which is facing up if you mount the PSU's fan down, was hot to the touch whenever it randomly powered down.
On a hunch, I flipped the thing around so the PSU's fan was facing up, which went against the manual's suggestions, and haven't had another random power failure.
Basically, if heat travels up, due to its lighter density, at least it'll vent out of the PSU's fan vent instead of collecting in the PSU's housing, like what was happening to me.
This may not be a panacea for all the random reboots for this model that I've read on the web. But, I thought I'd share my recent experience with this model in hopes it might help someone.
Regards