When going to its bed or workstation, a villager will not follow a path that crosses a dirt path block. That is, if it has to step down from a full size block onto a dirt path, then step up again to reach its destination, it will not follow that path.

 A repro world is attached.

Steps to reproduce:

1. Download and open the world "Villager won't cross.mcworld". This is a flat world containing a house with a bed inside and a shelter with a blast furnace under it. Dirt path blocks adjoin the door of the house and the front of the shelter.
2. Enter the command "/time set sunset" to make the villager go to bed.
3. Enter the command "/time set noon" to make the villager go to its workstation.

Expected results:
When the time is set to sunset, the villager goes into the house and gets in bed.
When the time is set to noon, the villager goes to the blast furnace.

Observed results:
When the time is set to sunset, the villager goes to either the back or the left side of the house, getting as close as it can to its bed. Since it cannot get close enough, it emits frustration (lightning bolt) particles, then searches for another bed, finds the same one, and emits satisfaction (green) particles. This repeats without end.
When the time is set to noon, the villager goes to the back of the shelter, getting as close as it can to its workstation. Since it cannot get close enough, it emits frustration particles, then searches for another workstation, finds the same one, and emits satisfaction particles, This repeats without end.

Additional tests:
If, while the villager is behind the house or behind the shelter, you give it a path of full-height blocks, it soon follows it to its bed or workstation. Sometimes there is a delay of a few seconds, presumably before it attempts to find a path again, but as soon as it does it will go straight to its target block.