The water and soul sand for my nether wart farm is behaving improperly.

When I use a dispenser and a bucket of water to flood my nether wart field for harvest, the field floods as expected, pushing items to the water trough at the end to be carried away for collection.

However, when the dispenser tries to retract the water, the source block disappears, but the water level in the field rises.  I can only get rid of the water by manually blocking out the four corners where the water is at highest level.

Below is a sequence of photos showing the progression.  The first is the empty field.  The second is the field flooded by the dispense as normal.  The third is the field "flooded" after the dispenser has retracted the water.

I have the exact same set up for other fields for other crops.  Only the nether wart farm  has this problem.  I assume it is an issue of the water interacting with the soul sand under the new bubble column physics.  If you look in the last picture, you can see an upward bubble column has formed where none previously existed.  All four corners will exhibit this behavior.