So I have a stage based on Call of duty Nazi Zombies and I had dispensers put behind 1 block to hide them. The path of least distance was where the items popped out. Which was downward.
It worked 100% of the time. So I expected the items to pop downward.

What actually happened was the items never went downward they popped out up and to the sides, aka the path of most distance.

1. Place a dispenser and wire it up to a button.
2. Make sure its up in the air.
3. Put a block in front of the dispenser then place a layer of 9 blocks 3x1x3(x,y,z) 1 above the placed block.
4. Then surround that dispenser and block with more blocks in the same shape as the above 3x1x3 layer. (This is hard to explain, im doing my b best)
5. Now 1 more layer of 3x1x3 under the placed block and punch out the center 1 block.
6. Now it should look like a 3x3x3 cube with a dispenser in the side and a hole in the center bottom layer.

Now this hole is the path of least distance(or resistance) and the item should just pop out on the empty space on the bottom layer.

ALTERNATIVELY you can move that dispenser outward 1 replace that spot where the dispenser was with a block then break the very center block of that 3x3x3 cube.
What it should look like is a cube with a dispenser on 1 of its 6 sides. with a broken center block on the bottom and 2nd layer.
So Now its easy to see that the least distance is to travel through that 1 block on pop out on the other side in the center of the cube. But it does not do this, it will pop out somewhere else.