I have merchants stuck on my map. They just froze in their tracks, for some reason, and they are just sitting there.
Here is what happened chronologically, in case it matters:
New embark, a heavily forested flat savage forest, with no z change whatsoever on the entire embark. There is a river running across northern border and murky pools litter the area. During first year, I get the "Wagons has bypassed your inaccessible site" message. That tells me it's that time of the year, so I plop down a depot and wait for the merchants to come and unload. I then trade them a pile of worthless bone crafts in exchange for two iron anvils and ten assorted logs. At this point, I call off my trader and stop paying them attention.
Then I get a message saying that they have embarked on their journey. But now it is mid winter and they are still around. It looks like they moved a couple of tiles and just stopped. The depot is also covered with some junk they haven't packed yet. I checked combat log and found out that a marksdwarf hit a giant mantis twice. Once on the embark day and once a day later.
But that is all. There are no corpses, no obstacles, no wagons, no messages. And the merchants are just standing by their pack animals, doing nothing.
Have you seen merchants behave like this? How can I get them to leave? What could have caused this?