I'm surprised no one answered your question yet.
The reason the door looks like someone kicked it, is because the door is locked into position until the player interacts with it.
The only workaround, that I've been using in my custom story is to duplicate the door, and set the duplicate to be inactive. Set the duplicate to be open by 0.15, or thereabouts, if you go too low, it will stay shut.
When you call the event, simply, set the original door inactive and set the duplicate active and use the prop impulse on the new door, not the original.
EDIT: Or, simply set the door you already have to be open by 0.15+ in the level editor