I have submitted a fix to Ultraprime to include in a future update.

The fix allows the reduction of packmasters to 0 if you upgrade the only packmaster to a master moulder in a unit of giant rats/rat ogres. The packmasters still show although the number listed will be 0. The packmaster will return if the master moulder is removed and the correct number of packmasters/master moulders/Skweel still works properly based on the number of giant rats/rat ogres in the unit.

As I said before I have submitted this update to be included in a future update, but seeing as I have had no contact with nor have I seen any posts with Ultraprime for a while I have no idea what is going on with future updates. Please understand that life gets crazy sometimes and beyond peoples control so patience must be considered.