North East Dispenser not remove dispensed water.

All 4 dispensers are facing down and have a water bucket, when triggered the first time, water is dispensed.
When triggered again, I expected the water to be retracted into the bucket.

However, the water is only retracted in 3 of the 4 dispensers.

Steps to Reproduce:
Build the 11 x 1 structure as shown.
Press the button, wait, and press the button again.

This happened in my survival world and in my flat creative world.

After further testing it seems to be related to the direction of the incoming and outgoing redstone dust.
1. If I turn the outgoing dust right (south), it will dispense water only.
2. If I exit the dust straight across, it retrieves the water only.
3. If I exit the dust left (north) It dispenses and retrieves the water.