Chip,
It’s likely that for the past five years the company paid your Mom’s share to others (or possibly to themselves within the working interest share). They’re now in the uncomfortable position of either coughing it up (the five years’ production) themselves, or recovering it from the others who had received a larger payment incorrectly. This is probably why they are delaying or attempting to ignore the situation. It may also be why they’ve suspended payment on a newer well (to accumulate enough to cover for past improper payments).
Having been through something similar I know this is a slow and maddening process to get them to act. The others have given you the best advice. You will likely need to bring an oil and gas attorney to get this resolved. 1) Make sure your paperwork is in order and provide the attorney copies of the court order, the document recorded in Mountrail County (if it was a separate item), and your letters (and emails) to the oil company. 2) Then have the attorney write them requesting why they’ve failed to pay you. Your alternative is to call or write the oil company every other week for the next four years. So unless your interest is tiny, hire an attorney. Even with a lawyer this may well take all year to resolve. Good luck.