Can't Select Expense Approver "Internal Server Error"

We recently upgraded to ERPNext v12.16.2 with Frappe Framework v12.13.0. Since we have done this, we are not able to submit an expense claim. As soon as we click our mouse into the “Expense Approver” field there is a warning message which says “Internal Server Error”. I checked to make sure that we have different employees which have expense approver status. This only became an issue once we recently upgraded to the latest version. Anyone else having this issue? How to resolve?