There’s a USB plug on the right of the MangOH Red labeled “console” (in small letters). You can connect to that; it will show up as a serial port on your computer which you can connect to using a program such as putty (on Windows) or microcom (on Linux). The serial port will print out some logging including a Linux boot sequence every time the chip reboots.
Actually can you attach the serial printout from a reboot? Also Legato logs a bunch of information to the Linux system log which can be accessed with the “logread” command. Can you send me that log from after the reboot?