How to Inactive Standard Service Invoice Form showing as Preferred form on Invoice

Hello,

I have a specific role that I want to remove a specific preferred form. Company-wide, there is a custom form that is preferred. I have disabled that form for my specific role because I do not want them to have access to that form. I went to Manage Roles settings and unchecked the Enabled box under Forms Transactions. Now I am successful at removing that company-wide custom form to my specific role. The weird thing is, the Standard Service Invoice form appeared as the preferred form for this specific role. I checked this standard form and it was Inactive. How