illagers will not path find to a villager on the other side of a wall.
To reproduce.
Build a wall 2 or more blocks high.
Place a villager on 1 side and a pillager or vindicator on the other.
They will not path find. Most times he will walk away and will not path find until there is direct line of sight between the 2 as seen in the provided screen shot. However a zombie will walk around the wall and attack instantly after being spawned.
Apparently this issue has been fixed in 18w46a.