To see if it was my baby who doesn't like car seats, I tried three other models (graco sunridge 40, chicco keyfit and britax b safe). I even rented one from a car rental during a 3 day vacation. The difference in comfort was very stark. I was able to transfer the sleeping baby and tighten him up without waking him in the rented seat. He showed no signs of discomfort in any of the other 3 seats. I finally ordered a sunridge, and have shot a video showing the difference in reaction between them. I also realized that baby's chin sits snug on the chest in mesa, due to its depth, which could also be causing additional discomfort, and i am always worried about him choking.
Its a shame that mesa is the priciest seat in the market, but provides no satisfaction guarantee and their reps don't own up the flaws in the product. I do think the fabric and material is very good quality, but thats not good enough to keep the baby happy.