I recently picked up 40.13 after a lengthy hiatus from DF, so I'm playing the game relatively "blind" to the changes since 34.11. I'm in the third year of my second fort (the first had to be abandoned in less than a year due to an inexplicable FPS drop) and I'm seeing weirdness with caravans. I think it's related to
bug 7185, but I can't figure out what could possibly be making the merchants freak out.
The dwarven caravan in the first autumn made it to the trade depot without any problems.
By the second year I had two depots set up -- the plan was to keep one depot locked down while the humans were visiting, then lock it down after they left and switch to the other for the dwarven caravan*. A dog managed to kill a kobold thief at the gates, but I was busy with other things so I left it there to rot. I noticed a sharp decline in kobold incursions thereafter, but when summer came around a human wagon passed through the gates, spotted the corpse and promptly transformed into a pile of cargo. This is when I learned not to leave bodies where merchants can see them.
I moved the skeleton well away from the gate. Yet come autumn, a dwarven wagon made it all the way inside the fort, touched the edge of trading depot #2, and turned into a neat pile of cargo while the rest of the caravan did a 180 out the gates. One of my dwarves was so inspired that he immediately grabbed the
wagon wood log and made a recursive amulet commemorating the settlement of the fort.
I thought maybe having two trade depots was causing the problem, so I deconstructed depot #1 and rebuilt #2. I noticed a
creepy crawler vermin corpse in depot #2 shortly after, so maybe that was the problem. Again in the third summer, a human wagon made it in the fort, touched depot #2, and became cargo. No sign of corpses or vermin anywhere.
This twice-a-year delivery of hassle-free logs to my treeless fort was nice, but I was really itching to do a proper trade
for reasons. The very first dwarven caravan had made it into depot #1, so I tried deconstructing depot #2 (turning it into a provisional office for my newly-appointed baroness) and rebuilt #1. To my surprise, this worked. I was finally able to make a trade in the third autumn. It's clear depot #2 is cursed, but I can't figure out why. It's a mirror image of depot #1, both depots are extremely well insulated from outside stimuli, there aren't any freakish monsters running around or puddles of blood yet, no clear hazards that would dismantle a wagon.
The only other difference is that in the two times the caravan survived, I waited until the merchants had begun unloading before ordering my dwarves to bring goods to the depot. Perhaps the mere sight of my dwarves is causing the wagons to suffer critical existence failure?
Layout of my fort:
bottom floor, caravan route in red
second floor
third floor showing trade depots, retracting bridges highlighted in blue
upper floor, depot hatches highlighted in blue
On an unrelated note, I have two barons -- the first inherited the position, then the second was appointed by the dwarf liason. Not sure if this is supposed to happen.
* Elves are extinct in my world, so there's no spring caravan.