The issue is caused due to incorrect data types in SmartEndpoint.
When an admin creates a WebRH account, or new preboot user, without expiration date, the server enters a record with NULL in the expiration_date field in the
user_node table in the DB.
Afterwards, if an admin updates these user names in "Users and Computers" tab, the server will override the expiration date for this user from NULL to 01/03/0001.