Upon deploying the vSAN witness appliance the appliance PSODs with:
The system has found a problem on your machine and cannot continue.
The password supplied does not meet the password policy requirements.
VMware vSAN (All Versions)
This is due to a root password not getting entered during the deployment of the vSAN witness appliance.
When you get to step 8 "Additional settings" in the Deployment Wizard ensure to enter the root password as it can't be left blank.