RESOLVED - Lenovo Thinkpad P1 freezing (1/2)

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   • RESOLVED - Lenovo Thinkpad P1 - Freezing (...  

My Thinkpad P1 is freezing sporadically, requiring me to power off the computer by holding the power button for 5 seconds. This can happen any time from 2 minutes after booting the computer, to many hours after booting. After one freeze has occurred, it is common for another freeze to occur within minutes after hard-rebooting the computer.

Conditions which cause the machine the freeze:
I cannot find any similarity in the conditions under which the machine freezes. Programs running at the time vary, but have been completely different.
The laptop is typically sitting directly on our dining table plugged into the power when the freeze occurs, but it has happened whilst on my lap on the couch
The other day it froze when literally the only running program was Firefox, and today it froze with only Chrome, PuTTY, HWMonitor, Cmd prompt (nothing running) and Windows settings window open.
I have been getting a lot of freezes recently when the screen turns black after a period of inactivity. Note that there was no screensaver set, and the machine was configured to NOT go to sleep when plugged into power. Therefore the only thing that should occur after inactivity is the display going black / turning off, but the laptop should still be running. When I come back to the laptop to start using it again, I am unable to get it to respond to input.
CPU, memory and disk usage are normal / not unusually high

Symptoms:
EXPERIENCE - The system all of a sudden stops responding to input from the keyboard, touchpad, trackpad or external mouse.
DISPLAY - Internal laptop display freezes with last image of the operating system and applications (there is no blue screen of death). It still looks like the computer is running, but it does not respond to input.
INPUT - Input from touchpad, trackpad, keyboard, external USB mouse do not exhibit any change to the display. Pressing Ctrl+Alt+Delete does not exhibit any response. Pressing Fn+Esc does toggle the FnLock light on the Fn key, pressing Fn+Space does toggle the keyboard backlight - this is the only discernable response I can get from the computer.
FAN - Shortly after freezing, I often hear the fan spin up to a faster speed.
SOUND - There are initially no noises or beeping. But after a few seconds I sometimes here the fan ramp up to a higher speed.
NETWORK - If use another computer to constantly ping the laptop over WiFi, the ping stops working after the machine freezes.
TIME - Leaving the machine in this state for 10 minutes does not resolve the issue
LID - Closing the laptop lid for 20 seconds (on battery or on external power) does not cause the laptop to go to sleep (the red light on the lid does not begin to pulse), even though it is configured to sleep on lid close on battery. Upon re-opening the laptop lid it is immediately on the same frozen screen (it never changed).
TEMPERATURE - See details below

Previous Troubleshooting:
Installed latest Windows updates
Installed latest Lenovo Vantage updates (including BIOS - details below)
Ran another operating system from second SSD - experienced the same freezing. This problem is therefore not related to the operating system.
Full scan completed by Windows Defender - no viruses found
Full Lenovo diagnostic run - no errors found.
Monitor the machine temperature with CPUID HWMonitor:
CPU temperatures range from 43 - 84 degC
SSD temperatures range from 28 - 58 degC
GPU temp ranges from 42 - 65 degC
Leaving the machine in the BIOS for a few hours did not reveal the issue, but the issue did appear when running in a different operating system. Because the system was not being used much in BIOS mode (there is not much available to use), it may not have been pushed to experience the issue.
Disabled superfetch (has been renamed to SysMain in Windows 10 v1809) - the freeze has continued to occur since this was disabled.

Operating System Details:
Windows 10 version: 1809
HyperV enabled, running a few VMs
Bitlocker full disk encryption enabled (software encryption with TPM plus password)

BIOS details:
Serial number = R90P26RH, Machine Type = 20MD
UEFI Bios Version: N2EET37W (1.19)
Embedded Controller Version: N2EHT25W (1.10)
ME Firmware Version: 12.0.24.1314
Display - Graphics Device: Discrete Graphics
Thunderbolt BIOS Assist Mode: Disabled
Thunderbolt Support in Pre Boot Environment: Disabled
Memory Protection - Execution Prevention: Enabled
Virtualization Technology: Enabled
VT-d Feature: Enabled
Secure Boot: Disabled
Intel SGX Control: Software Controlled
Device Guard: Disabled
UEFI/Legacy Boot: UEFI Only
CSM Support: No
Boot Mode: Quick

Hardware Configuration (changes from factory):
Addition SSD installed - Samsung 970 Pro 1Tb - Not configured in RAID - Used for second operating system, and is not in use at the time of the freezes