I had the achievement "Where do you think you're going?" pop up while I was back at base cooking shrimps, followed a minute later by the achievement "The hole". Looking at the radar, there was a blip way out on the west edge of the map by Yankee, but I didn't have remotely near enough stamina left to go check it out in person before it was gone. Whatever it was, I think there's a bug that allows wandering entities to trigger achievements.