Analytics not counting a large percentage of traffic
So I've been trying to figure this out for over a month now, but it is very clear that Analytics is not measuring a significant chunk of our traffic (somewhere between 30-40%).
Based off of every other form of measurement -- Ad imps, in-house traffic counters, Alexa Rating, Social media reach/engagement, etc. -- our traffic should be significantly higher than it is at the moment. It seems as if the issue is our Facebook referrals, particularly from desktop traffic. Facebook consistently generates between 35-45% of out traffic on a month-to-month basis, but in July that number dropped to 18% -- and no, our FB engagement didn't drop; it's actually been at an all-time high.
I have noticed that at the same time we began experiencing these problems, our crawl and page-not-found errors took a significant jump, too ... which tells me that something obviously happened, but I have no idea what that could be.
If anybody can help me in the slightest, or point me in the right direction, that would be much, much appreciated.
And in case it helps, our site is MileHighSports.com.