This particular issue actually was resolved on their machine. aanujan had 2 accounts on the box, they had 2 different user folders aanujan and aanujan(with the @hybidhub.lk), this was the state before the upgrade and this user was likely already experiencing odd behavior. When we went to convert this account there was a mismatch between the accounts.json and the User in Users folder. After this correction was made they were able to load the domain.
There was no problem that we could resolve as this was more of an issue with the accounts on the box before the upgrade, however, I did add in a more informational message for when this particular case happens. So it will provide a more helpful message than just "Object reference not set to an instance of an object."