Check to see if the device you are testing has both a bootstrap token
and secure token. FileVault enabled for all users, including any managed
accounts for Secure token. Check to see if there's a Bootstrap token by
running this command from admin acc...
@oandre3 Have you tested again with more modern system, and/or Monterey?
I've yet to find a resolution, even after trying the suggested tweaks
you've made.