When ever an item is pushed into a block from a dispenser or dropper, the item is always pushed out on the West side unless there is a block on the West side of that block.
It can be replicated with this simple setup.
You can also place the dispenser above or below the block and the same issue occurs.
This was not an issue up until the Snapshots for 1.8 were released.
This issue has been reported already. It has been linked to the original bugreport.
Please search before reporting any bugs, as it's likely that one exists already.