systemd user instance fails with "Failed to determine config file paths: Invalid argument" then "Failed to allocate manager object: Invalid argument" error messages

Issue

• When a user logs in, the systemd user instance (user@<UID>.service) fails to start and reports the following messages

  [...] systemd[4641]: Failed to determine config file paths: Invalid argument
  [...] systemd[4641]: Failed to parse config file, ignoring: Invalid argument
  [...] systemd[4641]: Failed to lookup StateDirectory path: Invalid argument
  [...] systemd[4641]: Failed to allocate manager object: Invalid argument
  [...] systemd[1]: user@1000.service: Failed with result 'exit-code'.
  [...] systemd[1]: Failed to start User Manager for UID 1000.