After a fire man killed my metalsmith during the first year of a new fort, I abandoned the fort and came right back in reclaim mode. I wanted to be sure the fire creatures were dealt with, so the dwarves would be safe in the future.
All went fine at first. Half a dozen archers made short work of the creatures. And then everyone set about picking up all the scattered treasure, and putting them in the right stockpiles.
But I eventually noticed that several craft items and a few rocks were not being moved. At least one stone was in the way of a wall being built. And there was one iron anvil left in the trading post that could not be budged.
I tried dumping, claiming, and everything else I could do, but nothing would get those things moved.
Then I noticed that the anvil still had a "[T]" after it, even tho the trading was interrupted when the fortress was first abandoned.
Near as I can figure it, the non-movable items were tasked at the time the fortress was abandoned, and the tasking was never cleared when the fortress was abandoned. As a result, some items could not be moved, because they were still "tasked" as far as the program is concerned.
It should be an easy fix, by just making sure that tasks are cleared when a fortress is abandoned.
For now, as a workaround, we can make sure the traders are gone, and that all tasks are killed before we abandon a fortress. (Just turn off all jobs for everyone, and them wait for any jobs being done to finish, before abandoning.)