Turkish Airlines Miles Discrepancy - Unequal Mileage Accrual for Same Flight

I flew with Turkish Airlines on the same route one week apart (same destination, ticket class, and ticket price), and while I received 500 miles, my friend received 1,250 miles. When I inquired about the reason for this discrepancy, I received no response. I learned that they can see our miles in their system and that they did not credit the miles we should have received for not upgrading our class.
If we are paying the same fare and going to the same destination, this is unfair. Who knows how many points have been erased in the past? It's disappointing. I expect a resolution for this issue.