Water not sucked up by dispenser

Found the bug in Survival, recreated in creative.
Multiple dispenser next to each other (2*4) , with a button one block higher. redstonedust on top of the dispensers.
When building SN, dispensers facing E the 4th dispenser (next to the button) won't suck up the water
When building WE, dispensers facing S the 5th dispenser (next to the button) won't suck up the water
When building NS, dispensers facing W the 5th dispenser (next to the button) won't suck up the water
When building EW, dispensers facing N the 4th dispenser (next to the button) won't suck up the water