I have two entrances to my present fortress, the main entrance, and a trader's entrance. The trader's entrance did have two sets of tripple doors between the trade post and the outside.
The human caravan had no trouble at all getting in. But while they were in, two of the doors got jammed open somehow, tho there was nothing blocking them. I used both the T and K keys to check them, and there was nothing holding the doors open, but they stayed open anyway.
And this caused strange behavior when the caravan tried to leave. It took several minutes for any of them to move, and when they did, they left WITHOUT their wagons. The people, mules, and horses went out, but the wagons were gone.
After they left, I removed the doors, with the thought of replacing them to fix the problem, whatever it was. But when I did, I noticed that the floors where the doors had been, were never smoothed. Not sure how, but they didnt "see" the rough floors on the way in, but did see them when the doors jammed, and they reverted to mules only, as if it was a dirt road. So it looks like a pathfinding bug(?).
Oh, and playing earlier, when they came in, I lifted the drawbridge behind them, to keep out goblins and kobolds while we were trading. But as soon as I did, they all tried to bolt and run, as if they were attacked. Thankfully I had saved the game when they were on the way in, and reloaded that save, and played it again, without raising the bridge. No problem. Least until the doors thing. So they were pathfinding a way out, even tho they werent even all the way in yet. They were in the trade hall, but not the trade post yet.
I was hoping to protect them while they were guests of my fortress, in case of invasions. What with a steam defense, a lava moat, a flood defence, and a very large pest-swatting drawbridge. I dont think anything will be getting in that way when its closed up. If I were the traders, that would make me feel a lot safer. But in game it has the oposite effect. (My main gate is where I will be "letting" invaders come in. It too has a steam defense, and a long narrow hallway full of traps. A hallway that can also be flooded. I just have to keep my own people from opening the door at the cave river end! And make sure no doorknockers get close to that door!)