Hi @Bigtiger welcome to the forum, i've been through the same problems importing door animations. I had to make my own armatures (exactly the same as any other door, so you don't mess with other armatures) and animate them, sometimes animations in 0 ad are exported incorrectly most likely very old meshes, and when you bring them to blender sometimes they change they position, rotation or scale.
In this case you could take any door from the mod Millenium A.D. wich are the most recently door armatures done by me itself, so you can guide yourself through the making of an identical copy of the armature so you won't have another headache.
Armatures after being exported they won't accept any modification you made, so the armature will have to remain untouched, But you can alter the mesh.
Always save the blend original file when making new armatures or animations.
Save every animation as actions.
for repeating animation always make a loop of the first and last frame.
if you can guive me references i can help you with your problem.