Every Vortex product I've owned has crapped out. I'm surprised to see this many reports from other people having trouble with them, normally when I've reported bad feedback I've been bashed and everybody else in the world has no issues with them and it's only me having them fail as if I'm lucky enough to have gotten all the bad ones.
Honestly it's common with the majority of scopes made in the phillipines or china though, not just Vortex. Vortex just happens to have their entire lines except the highest end Razor's made in those two countries. Even the Razors have failed though. I've only owned one Razor and it was the gen 1 and it failed on me. I have a couple friends who have sent in gen 2's for repair too. One friend of mine has a gen 2 3-18 and it's the only Vortex product he's ever owned and it's needed to go back for almost a year now after the erector/reticle assembly let loose inside for the second time. He had to send it back before he even mounted it too because of an issue with the turrets. He hasn't sent it in yet because he's frustrated with it and just doesn't shoot much these days but he's already said that when he does he's dumping it cheap and buying a NF or S&B for that rifle.
There's a lot of people who swear by them though and say they have never had an issue. Not sure if they're just getting lucky or don't use their stuff much, but good for them either way. If I could get lesser expensive optics that had satisfactory performance, the features I need, and good reliability I'd be all for it but my findings are that it doesn't work like that.