In this save I had a were-horse enter the map.

I took my military (two squads) and using squad commands, ordered them to attack and kill the beast.

Both squads exited the fortress and proceeded to the NW corner of the map (top left) pursuing the creature. In the process they forded the small brook with no problem.

The were-horse disappeared and I got the "no valid target" so I cancelled the orders in the squad window.

At this point both squads remained jammed at the NW border and would not move. I used the squad window to station them near where the bridge appears. They did move to that station point. They would not under any circumstance ford the brook again. You can also note stairways to the north and south of the brook. Thinking they were stuck I ordered miners to dig a passage and to also build the bridge. The bridge was build by the military after changing some of them to Architect/Carpenters but my regular Arch/Carp and Miners did not approach that area and in fact show up as No Job in the listing. It appears this area is blocked off somehow.

I've further gone and deleted both squads in the military screen and then reconvened them both. I've saved and restarted the game. All to no avail.

At this point the military are unhappy. They've left gear scattered (they removed it when I deleted the squads but haven't picked it all up yet since I reactivated them...probably due to the over/in place of clothes issue.

I don't know why they are stuck..there is an obvious pathway. But with miners not approaching the area it's obvious the area is blocked off somehow.

No burrows...