This post has been bothering me for a while now. I think I know why. We purchased a 2015 36qbok a couple months ago and during the inspection something caught my eye as a problem but it did not register all the way till this posting. We know the manufacturers cut as many corners as they can and this is one of them. not that it is bad but not the best way of doing things.
This will get a little deep and I am no way a physics person but the concept is cool to think about.
I have attached a pic of the problem.
With all things equal water will not flow do we agree?
So water flows because of differences in pressure.
You sucking on a straw in a glass is simply the atmospheric pressure pushing the beverage up the straw not you sucking the liquid up the straw!! you can prove this by trying to drink out of a sealed glass container good campfire fun..
OK back to the problem. Water has a weight and gravity acts on a column of water increasing the pressure at the bottom of the the column. Take the stairs at a hotel and look for the red pipes they usually have gauges on them at each level. Now this water is under pressure but you still see the added pressure caused by gravity.
When the tank fills and seals off the drain pipe from the sink then water is not able to flow into the tank as the pressure increases due to the lack of venting caused by the install. See pic
You will see in this pic the line from the left is the sink drain going to the Y then the line going up is the Vent going to the roof and the line to the right is going to the tank. this view is under the stove. If you open the spice rack you will see the vent going to the roof.
I believe that the cause of your problem is due to the drain pipe extending down into the holding tank too far.
Now the next question is why.
Has tha tank moved?
Did they make the pipe too long from the factory?
The only way to find out is to drop the belly to verify the tank is in place or pull the drain out and measure the pipe.
Hope this helps I know I had fun