Why does the same player have different scores for the same Game Week?

Scoring for a player depends partly on that player's position. 

When Sorare cards are minted, the positions on those cards are permanent. For example, if a striker later becomes a midfielder, any cards for that player minted as striker cards would forever be scored as striker cards. Future cards, minted as midfielder cards, would be scored as midfielder cards.

Whatever the card says for position is how that card will be scored.

Player pages will always reflect the player's current and actual position.