Sounds like DSS (Dirty Sock Syndrome). Realize it can be difficult to fix, more often than not symptoms are treated only to return a short time later.

Can't help you any more than that because it is a "hands on" problem.

I looked that up. They say the coil is clean. Its a brand new system and house, they keep blaming it on a hot attic saying the coil gets too wet due to excessive heat, nobody can figure it out? It's almost like the attic air is seeping down. Ventilation? Could that cause the AC to fail??

New home builders are the worst with serious problems like this. It would be best for you to hire a separate HVAC contractor willing to figure it out.

Technicians will most likely guess at it or more likely just blow you off, suggest the problem will fix itself or some other nonsense type excuse. You need to find a "working" HVAC contractor and hire them to investigate and give you options to solve the problem.

Guessing doesn't fix anything.

"Guessing doesn't fix anything."

Bumper sticker for tech tool chests? Should be.

My house has the vents in the attic and there's never been an unpleasant odor from them; the only issue with it in an older, not well insulated house is I think a lot of $$$ is wasted up there.

I would wonder, could condensate somehow be pooling in the system w/o draining and thus causing mildew growth? Even though condensate is hypothetically deonized water, as a practical matter a lot of ions are flying around the air of your house and with a very high quality Hanna meter I've tested such water at around 30ppm - plenty to support microbial growth. (I've worked in labs and have seen green algae manage to grow in the receiving tank of an industrial grade steam distiller, just from ions left over from the tap water rinse. To stop this, we had to start triple rinsing the glass jugs in distilled water)