If sand got in the scope then it's not sealed and will fog up. That's serious. Means you have regular air in the scope, not a noble gas. Otherwise sand can't get in it.
Probably got in there when it was assembled. Shit happens I guess. And they don't test 'em in full sunlight for some reason so QC misses a lot of shit. I bought an ACOG on Ebay. When I got it, it had a hair or a crack in the glass and some other debris along with a smudge at the bottom of the reticle.
Turns out the guy I bought it from, he sent it back before selling it just to make sure he was selling a good scope. He was trying to be honest. But turns out THAT'S when they fucked it up! He sent it in for inspection prior to sale, they send it back in worse condition. I call 'em up and shot the shit a bit and let 'em know I'm a vet (it's the difference between a 1 week turnaround and a 1+ month turnaround!). Same week I got it back, like new.
Send it back. Something's wrong and needs to be fixed.