Villagers cause massive tps lag when trying to pathfind. They bob up and down in a 1.5 high hole and every time they do so, this causes a massive lag spike indicating their pathfinding efforts (from the profiler).

Capping them with top slabs resolves the issue by cancelling their pathfinding.

Single pathfinding routine seems to cost way to much? Villagers in the attached world are close to Y0. Is void air properly treated in the pathing algorithm?

Lagspikes are most prominent during the night - when they try to pathfind to their beds.