Why is the charge account not defaulting from the user's preferences?

We have a multiple requisition BUs. For all but one, the users' charge account primary in favorites is defaulting on the requisition. For this one BU, there appears to be a blank record along with the charge account(s) in the preference favorites. This occurs if there is one favorite or multiple favorites.

I have look through support documents but cannot find anything that points me to a possible cause.