I don't know why it has changed from previous versions but according to the Administrator Guide the LIST method applies to the Field object. So you're line here
If Not Cust_isInList(Bug_Fields("BG_STATUS").list, Bug_Fields("BG_STATUS").value) Then
should work, I think, if you change it to
If Not Cust_isInList(Bug_Fields.Field("BG_STATUS").list, Bug_Fields("BG_STATUS").value) Then