When a hopper minecart is slightly clipped into a block beside it it will not fill from a chest above.

This bug is positional. It occurs only if the hopper minecart is on the west or north side of the track (lower x or z coordinates).

Steps to recreate:

1. Build a track as shown with the single powered rail at the west or north side. (Or open the world attachment).
2. Place a hopper minecart on the single powered rail. Any items placed in the chest would currently work.
3. Push the button.
4. When the minecart comes back to a slightly different position items in the chest will no longer flow into the minecart.