Strange thing in my case.
I have RB333 RouterOS v3.10 that was randomly rebooting with that error (+ watchdog timer one) during approx 1 month, and it stopped ~18 days ago. When I log in the ONLY difference I can see is this:
system routerboard print
There is no info about current firmware! I am sure it is v2.15, but I dont know how that info could be lost. I dont want to do anything for now, for it's functioning well.
system resource print