Master Water Conditioning sells to a lot of plumber and pump supply houses. Was the guy that came out a plumber? Plumbers tend to not know much about water treatment or the equipment they sell and rely on the supply house personnel for support, which can be rather poor.
The sulfur mineral can be Pyrolox or manganese greensand. How old is the equipment?
Is the time of day set correctly and staggered so no two pieces are backwashing or regenerating at the same time?
Post pictures of the control valves and then the equipment so we can see the order from the well pressure tank.
The hour glass piece is a combination/over under filter softener and Master used to use only Autotrol control valves but went to Clack a few years ago. The prefilter ought to have the cartridge removed so the equipment gets full pressure and water flow. The sulfur filter does a better job than the disposable cartridge does, and so does the the acid neutralizing mineral.
Or you could have a bacteria problem causing the odor. Have you had a Coliform bacteria test lately?