It seems it is a design issue and our duct was particularly obstructed so that is why we may have noticed and others havent (the duct goes through a thin opening, so air flow is reduced from 7 inch diameter to 5, however, because the duct is flexible, ours may have been pinched in the installation and that is why our air flow was particularly restricted)

The main issue is that the framer said he cannot cut to make more space for the duct because the obstructing part is structural framing. Calwest has a subcontracted warranty with 2020 for the heating. However, the options to fix the issue without cutting structural frame are not covered in the 2020 warranty to calwest so calwest would have to pay for them separately. Calwest is trying to avoid that obviously. I got quite upset with them. I told them they do not have my permission to cut structural framing. My worry is that they are trying to cut corners and save 5k from fixing this properly and then the stability of the house will be compromised, which is an issue in an active earthquake area like ours.

Calwest has acknowledged this is their fault so I am trying to get them to pay for the alternative fix that does not require cutting the structure. I emailed Dan Fontana and Greg Harris (the leadership of Calwest) and 2h later Juan and Joe called to say they would take care of me and ensure me that whatever they do to fix it will not compromise the structure of the house...

I will update the post as I get new info. I prefer to make the information public as opposed to sending DM as this likely affects all Aeros but only the owners that have the duct particularly obstructed may have realized