@Shortt5  did you try to right-click the number  on Form 3800 Line 30 and select Cross-Reference.  on mine it was automatically filled in with the solar credit from Part III of 3800.  there is no double counting or manual typing of the 3800 needed, so i'm not sure how else you can find the source of the doubling.  try the cross-reference and see if it shows up with the forms/areas the number is pulling from