[NaS]

Код:

TruckerTogetther[playerid] = INVALID_PLAYER_ID;
TruckerTogetther[TruckerTogetther[playerid]] = INVALID_PLAYER_ID;

You set TruckerTogetther to INALID_PLAYER_ID and then use it as index.
That's your index out of bounds error.

Store the first value in a local variable, then reset it for playerid and after that use the local variable to reset the other player's TruckerTogetther index.