In MP score player returns only the score of player in faction he joined first (within one server session).
I.e. if he first logged for WEST faction and then relogged for another faction, score player will show his score when he was WEST, no matter what real score is in current faction.
In this regard it is better to use getPlayerScores:
(getPlayerScores player) select (count (getPlayerScores player) - 1)
or
(getPlayerScores player) select 5
- it will always return the player's actual score in the current faction.