Hey;) I tried going through door and the message was that it was closed, you need to meet some conditions.
There wasn't any boss here like you mentioned.
Turrets had message that those vaporized but crawlers had something like "crawler was knocked down" after noone was coming towards me i tried shooting crawlers and i got message you shoot crawler but there wasn't any message that it was knocked down. Maybe i need to shoot many times to vaporize it? But I thought something was wrong, because no crawler was coming or attacking me and I spent some time there.