Honestly I'm not surprised at all assuming the base is made from aluminum...
Aluminum is quite soft and the aluminum used on my tepui, and I would assume on your CVT too, is a pretty soft aluminum.
I've noticed in the past when cleaning out my tent after a trip, when I have the mattress out and the base is exposed, that you have to keep your weight on the internal supports of the base otherwise you dent where you put your knees.
Seeing how only a 2.5" foam mattress is covering the aluminum base (unless you have an anti-condensation mat) I'm not surprised at all that the base begins to sag between the supports. When crawling around in the tent on your knees or feet you put a lot of down force in a small surface area which would dent the base.
Manufactures could use a higher quality aluminum (just like the Tepui Ruggedized or the CVT Summit Series) but that only adds to the cost of manufacturing, shipping, and the overall weight of the product which every manufacture is trying to keep to a minimum to satisfy the consumers needs. Not to mention the added manufacturing costs of a more resilient base material would translate directly to a higher MSRP.
I guess you have to pick your battles.
Just my thoughts on the complaints.