Not necessarily a bug per se, but unbuilt structures (just placed by the player) seem to have just as much HP as a fully-built one. I abused this to instantly create a triple-layer of walls to defend against masklings. Pretty effective. Should probably be fixed. Most games have just-placed structures at 1hp for this kind of reason.
Another one: the pigs have escaped their pasture and I have no idea how. Nobody seems intent on putting them back either.
Edit: The pigs mostly got re-gathered eventually, but one dude got stuck on a peninsula while gathering pigs (again), which seemingly stopped all pig-gathering business altogether, despite half a dozen empty pastures.
1.3 has an overallocation bug around pigs and tradehouses. When a group of pigs reaches the tradehouse, another batch of pigs is sent out. That's been fixed in 1.4.
There is currently a limit of 1 shepherd per settlement as well, which is why the stuck guy is preventing any other pig gathering. Could you send me the world so I could see how he's getting stuck?
After reloading the game it seems that he got unstuck somehow. He was at the tip of that peninsula while he was stuck. I don't recall having tradehouses when the pig escape happened but maybe I'm wrong.