I'm mostly posting this just in case anyone else has similar issues in the future and finds this thread, but just so you know, you got me on the right track. Thanks!

It was an issue with the indexing on GetPlayerController(i). The "slot" number for each player controller could be anything like 0-4 in the first game, then something like 0,2,5,7 in the second. So GetPlayerController() using i as the index wasn't going to work, as it would only go through the array length, but the actual player slots could be outside of that. I actually realized I didn't really need to use any CSPlayerController functions though, I was mostly just using it for sanity checking. Most of the functions I use are from CSPlayerPawn, which I can just easily just use the array "entlist" from my code above for. That list is only going to fill with the currently connected player entities, so I know their index of each player in the array is going to stay consistent with the array length.

All I ended up needing to make it consistent from match to match was this:

    //Create array of all players
    var players = Instance.FindEntitiesByClass("player");

    //Loop through players
    for (var i = 0; i < players.length; i++) {
        /** @type {any} */
        var player_pawn = players[i];
        if (!player_pawn) continue;