I hate when doors get stuck like that. Worst bug ever, seriously.
One trick is to 'overload' the door with your Energy Link. It usually reopens it. But you need to have access to the plug for that...
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Hard to tell what happened in your case though OP. Like Northpin said, this problem seems to be less frequent when doing missions in single-player.
But it's a real nightmare in multi-player CZ. It happens a third of the time and breaks the gameplay badly.
It's seems to me that it's related to networking when you're in multiplayers. Kind of feels like a double instance thing indeed.