Device has been locking up once a day, requring a restart.

Went though Support, they want to send a tech out... 

I seen this in the log though when the internet goes out...

31.12.1969 17:00:30 Current booting firmware version is 2.21.01_build03

31.12.1969 17:00:30 REBOOT REASON is 2

31.12.1969 17:00:30 REBOOT TIMESTAMP is 0


The time resets, and then it says "reboot reason is 2" 

What is reboot reason 2?