Relogging causes mobs between fence hitboxes to glitch through blocks

With the setup shown in the pictures, of a diagonal water stream pushing villagers in between the hitbox of an unconnected nether brick fence and any kind of unconnected wood fence, with full blocks or half slabs (only ones tested), logging out and then back into the world will cause the mobs to glitch through the slabs or full blocks they are pushed up against. In the pictures I switch between the use of glass and barrier blocks for better visibility.