The NPCs are locked inside...
I tried to go in.. and succeeded but it will not let me leave, neither door works.
It just gives the animation for the door opening but does not exit you to Whiterun.

Not familiar with this glitch but I have encountered a door that was left open, and after I activated it, it closed, then I was able to activate it again and leave. Try loading a previous save and re-enter Warmaidens and see if it fixes it. If that doesn't work hopefully someone else will be able to help more than I can.