iMac Crashing – Fix iMac 14,2 Crashing After 10.14.2 Upgrade

Just upgraded to 10.14.2 and my iMac won't stay up for more than a few minutes. I've seen some chatter around about crashing on sleep, but I've disabled sleep and the crashes still happen. I've only seen the crash once myself (it's usually at the FV login screen when I come back to it).

There are many /Library/Logs/DiagnosticReports/*.shutdownStall files. I ran spindump -i on them, but didn't see anything useful.

Here is the output of log show --predicate 'eventMessage contains "Previous shutdown cause"'

Timestamp                       Thread     Type        Activity             PID    TTL
2018-12-15 09:20:47.803777-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 3
2018-12-18 07:39:32.816241-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 3
2018-12-18 20:23:39.848421-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-18 20:32:21.839740-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-18 20:36:39.852220-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-18 20:42:35.819973-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-18 21:55:13.823707-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-19 07:35:41.854712-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-19 08:38:28.813974-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-19 08:45:51.834954-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-20 07:40:27.803518-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-20 07:47:46.849858-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-20 17:35:21.830622-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-20 18:14:37.842271-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-20 21:51:11.880126-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-21 08:07:24.805766-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-21 10:28:19.805956-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-21 11:23:36.798586-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-21 12:04:43.882547-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-21 12:32:17.812293-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-21 13:25:26.868364-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-21 21:55:40.848997-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-21 22:01:35.808202-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-23 08:36:34.842667-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-23 08:46:37.867699-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
2018-12-23 09:20:59.865468-0800 0xaf       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -128
--------------------------------------------------------------------------------------------------------------------
Log      - Default:         26, Info:                0, Debug:             0, Error:          0, Fault:          0
Activity - Create:           0, Transition:          0, Actions:           

Googling around, it looks like -128 shutdown code is unknown (maybe memory). I'm mainly posting this before I go to all the trouble of assuming it's bad memory or something and not a bug in Mojave.