I still need a screenshot, because I checked the kismet, it doesn't have the problem.

Okay so I was kinda wrong. All the doors are initially open. However, it appears that around Wave 14, at the end of the wave, the doors to the arenas swing "open" causing them to phase through the walls and stop at an angle that just barley allows the player to go through them. This will occur again, at some point (i think it's if the next time the arena is played on), which causes them to "open" again and prevent the player from going through.
I don't know how much you editted the map outside of the listed features above, but I think it has something to do with the fact that the map was never meant to be played endless on, thus it's just a natural bug. I also don't know if it's Wave based, random, or caused by replaying the arena multiple times. If it also helps, I tested this on Random.

which door?

There's a bug or something where the doors to the hatches aren't open enough to allow the player to go through them on certain arenas.

Fixed a bug that teleport player not in volume will not teleport all players if the server have more than 6 players.

Endless probably work best on big map cause small map like this kinda small.

Added hints.

My country doesn't celebrate april fools

How do I even start this? I spawn in a room to choose Serial or Random with values of 20 on each but have no clue how to initiate either of them and you don't offer any explanation. Also I noted this was posted on April 1st, so is this map a joke?