Make a player manager device. Put a map object in it. Put all your spawners in it (the device) as editables. (Make sure you add 1 more spawner than the maximum number of players.) Subscribe to player added, player removed, and player spawned events. When a player shows up (either by spawning in or the player added event), see if they are in the map and if they aren’t add them. When a player leaves (player removed event) find them in the map and remove them.
The map object is your “list” of players. Look them up using agent to get player, then use player as an index to get your “custom” player object that has all of the stuff you want to keep track of about the player. (You’ll need to make a unique class for that.)
There should be videos on YouTube about how to keep track of players (via custom player maps). Look up Warforge, Graeme Bull, and there are probably some others.
In regards to my comments about fort_character, if/when you find yourself using GetFortCharacter[] (for a valid reason, of course) - just make sure you use IsActive[] on the result to make sure it is actually valid.