As I hate to admit it, I ended up switching to an Aluminum bottle from MAC's Radiator (they are local to me).
I didn't have an issue with caps anymore once I switched to the Volvo, but bottles started giving me headaches. I was buying new ones once a year it seemed. Because of the expansion and contraction of the bottle, they seem to develop cracks easily. I tried all different brands (besides MOPAR OEM) and all seemed to have the same issue. It may be issues because of where I live as seasons are well defined. (100 degree summers and snowy 25 degree winters)