MacbookPro Retina Late 2013 - Random shutdowns

For the last few months computer has been randomly shutting down. I have tried to diagnose the issue and notice that the computer works fine if a Thunderbolt Display or Thunderbolt Ethernet adapter is connected, random shutdown if nothing is connected to Thunderbolt. Also works fine if booted into Windows Bootcamp.

Took to Apple Store Genius who ran hardware diagnostics, reset NVRAM and SMC, no problems found. Suggested I back-up computer and reinstall OS, which I did. Problem still occurs on virgin as if new computer.

On a second visit the Genius wanted to keep computer for several days to run deeper diagnostics. I may do this when I have vacation scheduled.

Here is a snippet of the log file showing the point of shutdown with 2021-11-30 10:40:00 -0600 ShutdownCause           SMC shutdown cause: -128:

Power Management logs:

  Source: /usr/bin/pmset -g log

  Size: 66 KB (66,445 bytes)

  Last Modified: 11/30/21, 10:44 AM

...

2021-11-30 10:37:14 -0600 Assertions              PID 583(studentd) Created NetworkClientActive "studentd:583:CRKNetworkPowerAssertion:0x7fbb4e722120" 00:00:00  id:0x0x1100008c35 [System: DeclUser NetAcc kCPU kDisp]          

2021-11-30 10:37:19 -0600 Assertions              PID 583(studentd) Released NetworkClientActive "studentd:583:CRKNetworkPowerAssertion:0x7fbb4e722120" 00:00:05  id:0x0x1100008c35 [System: DeclUser kDisp]          

2021-11-30 10:40:00 -0600 ShutdownCause           SMC shutdown cause: -128:                                                                

Sleep/Wakes since boot at 2021-11-29 16:46:56 -0600 :10   Dark Wake Count in this sleep cycle:9