Well attackers spawn right above that area so if you were a defender and someone was hitting you it could be they were standing up top? So they could get the angle to you over the forcefield?
Hmm... don't you have to wait for at least one of your teammates to reach the spawn area (i.e. the location where you get the convo saying "you have breached the cargo bay...") before you can successfully respawn into that next room? Usually when I've respawned before a teammate has reached such areas (as an attacker), I end up respawning back in the previous room.