Update 2: The dwarves don't seem to be
frozen anymore per se, but (unless I just don't understand dwarf fortress combat) they don't seem to be doing much. They'll dodge attacks, but apart from my markspeople they won't attack. There are more announcements now also, including dwarves cancelling jobs due to not finding a path.
I doubt there is a syndrome that might cause these things. Have you cleared all burrow designations or assignments?
I don't currently have any burrow assignments...
I would try removing them from the military, re-assigning them, then ordering them to move around and see what happens.
I thought this might work... but it doesn't seem to have any effect.
It might be the case that these three dwarves are assigned specific weapons, instead of say a uniform, and are desperate to re-acquire whatever sword or shield they lost in the fight. Changing equipment might help this.
They're assigned a type of weapon (warhammers and spears, not sure if that's what you mean by specific weapons), I would imagine unassigning and reassigning them to the squad would fix it if this were the problem, but it doesn't seem to fix it. Thanks for the suggestions though.
The fact it's cancelled due to not finding a path would lead me to believe something is blocking a path, or they're going for an item that's out of reach for some reason. Dwarves tend to replace items when a better one becomes available, so did the dead dwarf maybe drop a high quality item the three might be going after, but the item is in an odd place?
This was my initial thought as well, especially since some of my dwarves have no armor at all (I've got tons of silver, but no iron or copper), they might be trying to pick up some of the salvaged armor of dead dwarves. That being said I'm not sure how the path could be blocked, the military dwarves made their way to the beast to begin with. Thanks anyway.