I liked how you used instance then said for instance, that confused me for a sec. Anyway...
I would approach this by matching them up as follows. Doors have IDs, but don't pair them in that way.
Door A, the ID is 0.
Door B, the ID is 1.
Lets say they work as A goes to B, B goes to A like portals.
You have a variable on the door additional to ID, something like GoTo.
Door A, ID=0, GoTo=1.
Door B, ID=1, GoTo=0.
When you overlap a door, you teleport to a door where door being overlapped.GoTo = door.ID.