spawns in multi

[Element]

I was hosting a deathmatch game on the map DM:Titan. I had the default scout as the only selectable vehicle. After a few minutes into the game scion scouts began to spawn randomly on the map. Then a ISDF Tank spawned. After the tank had spawned a player who had joined was playing when he started to get spawning tanks as his defualt vehicle, no scouts would spawn after he died, only tanks, even though they were not on the vehicle list. What causes things like this to happen?