There have been a few reports with auto reboots on the USG-PRO-4 and ER-8.
After reviewing this with our RMA team, the simple solution is to make sure the units are on the latest firmware. Please make sure this is being done before a RMA is submitted as this is the quickest solution.
More info can be found here:
*UniFi* - INFO
*EdgeRouter* - INFO
All new hardware shipped within the last month should be on the latest firmware.
Thank you!