Pathfinding prefers North (negative Z) direction

This problem existed a long time ago, then seemed fixed... but has now returned. It's doing the same behavior for me on a friend's server; our fenced-in Iron Golems are all just wandering gradually into one corner.

Also having this problem in 1.14.4. Cows, Pigs, Sheep, Chickens all are affected for me. My farm is in the negative/negative quadrant and they keep clustering up in the northwest (further into negative/negative) corner to the point that most of the other space is empty.

Are you sure it's not because of spawn chunks? Animals tend to walk out of spawn chunks, where they freeze, making them all get stuck just outside the border to the spawn chunks.

For me it's definitely not – it's happening to me at around -1400 -1400 while I'm in the area and everything is loaded.

This is happening to me as of at least 1.11. Still happening in 1.14 too.

Seems to happen to Cows, Sheep and horses. I haven't really noticed it as much with other mobs but as OP stated, this will required more testing.

From what I can infer watching the animals in my screen shot is that they wont give up pathing to a point and as such they get bunched up and end up cramming in the SW corner of any pen I create for them.

Update: Pigs are now starting to cluster too. They are less prone to it due to how the fences are placed in my village. But I definitely see them hit their farthest SW corner then change directions but get blocked by other mobs pathing there as well causing them to bunch for a bit until the entire group pushes each other around enough to free the ones who got to their point.

You can sorta see this in the Sheep and Cow pen. Notice the one crammed into the corner is facing NE heading and the rest are still trying to shove into the SW corner.

Seems to indeed by fixed for me in the latest snapshot. My usual test no longer has most horses bunched up in a corner, instead they sometimes make little groups anywhere, sometimes spread out again. That seems intended.