I couldn't find this in the search, I did find something about the trade depot accessibility bug in regions with cliffs (where they keep claiming that your depot is inaccessible when it is not) which might also be somewhat related to this, since I am in a cliff rich area and also experience that bug. But that's not all.
I always use a funnel system with forbidding and allowing doors, and a meeting area between those doors so dwarves can go in and out without there ever being a direct entrance to the fort. This has always worked. Now I have the problem that migrants don't go to the meeting area. I have no meeting areas outside, and the only one accessible from outside is that particular meeting area. They just stay completely frozen at the edge, as do any pets, sometimes one or two dwarves move to make room for the third but thats it. Even when I set it to 'dwarves stay indoor' it doesn't do anything. Making a clear entrance by allowing both sets of doors causes them to run inside as normal, but I wonder why the system that never failed me before suddenly doesn't work.
But that's not all. I have a river outside. Yet the migrants stay frozen on the spot even when thirsty, and eventually die where they stand, unless I open the door or set them to military and order them to patrol the funnel area (which works so I'm positive it's not inaccessible). So I can circumvent the problem by drafting every single migrant and sending them inside, but still, it's a bug.