Mojave update 2020-002 - reboot on sleep

I am using a 2018 Mac Mini running 10.14.6 with security update 2020-002. 32GB RAM.

Ever since the update, when I put my Mac to sleep - or if it goes to sleep on its own - the machine shuts down after it has gone to sleep, then reboots.

I have done the prescribed resetting of the SMC; I have reset my ethernet adapter (which is my primary network connection), etc. I have not been able to get the machine to successfully sleep.

I should add: when I run

log show --predicate 'eventMessage contains "Previous shutdown cause"' --last 1h

I get:

Timestamp                      Thread    Type       Activity            PID   TTL 

2020-03-26 13:48:37.482116-0400 0xc3      Default    0x0                 0     0   kernel: (AppleSMC) Previous shutdown cause: -20

I have also tried reinstalling 2020-002, and I did an Internet recovery to an earlier state. No change. Then I reinstalled 2020-002 once more. No change. Is it possible that my Mac's firmware got corrupted during the update? (This update behaved in such a way that made me feel like there *might* have been a firmware update, even though it wasn't specifically called out or documented anywhere.)

I have not seen this behavior reported since the update came out. Is anyone else experiencing this?

Drew