Dishwasher air gap smells bad...

[lizard]

and there is a little bit of water always left at the bottom the hose that leads from the air gap to the dishwasher, it's clear so I can see it.

There is also some water always left in the bottom of the dishwasher but it doesn't smell.

A plumber came out already and replaced the motor that pumps the water out but it still never completely drains.

Is there anything I can do or do I just have to have the plumber back?

Thanks!

 

[Geofd]

the hose coming fron the dishwasher drain to the sink drain should be looped up as high as possible before entering the drain that allows water to drain properly