Villager pathfinding breaks when large numbers of lower half slabs are used

i have an underwater dome village and recently attempted to limit slime spawning by using lots of lower half slabs... but now my villagers dont move, they stand it place and target me forever. 

expected behavior: walking around, refilling at workstations, etc.

observed behavior: None, no AI is observable in villagers.

note: a raid worsens this, but it continues to be present whether or not a raid is occuring

short clip https://imgur.com/H9lWGw3