I have 0702 board (doesn't boot from just USB power; sometimes gets stuck at CPU VDD uboot line) and also started experiencing this reboot issue about a month ago. Before that it was happily working for months without any uptime issues, even during rather hot days (~40C). It may have coincided with the room it's in getting relatively chilly in the nights (~5C).
@mu-b, you seem to have put an amazing effort into investigating this. Thank you!
Have you been able to:
Get GlobalScale reply on this matter?
Increase voltage with custom U-Boot? My board also reports "CPU VDD voltage: 1.050V"
Is there anything I could try to help with?