My issues were exterior fogging as well. I realize that there are a lot of variables, that being said my razors did not fogg in the same environment.......could be as simple as eyepiece design
My 10x42 Euros fogged up on both me and my hunting partner on a September elk hunt. I spoke with the guys at the optics counter at Cabelas and they said it is common with binoculars in cold temps, I told them that I disagree have not experienced this with my 8x42 conquests, or 12x50 razors...