Can't remove unwanted attribute from the request form

I have a request form called "Office 365 New Shared Mailbox Request - Form" in "Client Support" ticketing application (form ID 3117). Originally, it had a number of attributes that were removed from this form, and replaced with other attributes. These attributes that were removed form the form, still exist on the global list of attributes because they may be used by other forms. However, I went through each of these attributes and made sure that the ticket type "Office 365 New Shared Mailbox Request" that is associated with this form is NOT checked in the "Associated Types" section. Although these attributes are no longer visible on the form when I edit it in Admin Designer, or when customer opens it on the Client Portal, one of them creeps back in when an existing ticket created with this form is opened for editing in TD Next client (see attached screen capture). The attribute that exhibits this behaviour is called "UWinID" (15733). How can I ensure that this attribute does not show up on the ticket when I edit it in TD Next?