As X is not a factor, then this appears to be a "hang". That's narrowed it down considerably.
You could re-install, or upgrade, whichever you find convenient. However, you may still be able to obtain possibly useful information from the 4.8 system if you can force the kernel to enter ddb or to execute a crash dump. (This might be via the sysctl ddb.console or via the machdep.kbdreset sysctl, as applicable.)
Just finding out where the kernel may be looping might help isolate a root cause -- for example, if the kernel is looping in a hardware driver, that might be indicative of a problem with that hardware component.