Magento and Analytics issue help?

Anyone come across a scenario where Magento and Sage are pulling wildly different numbers for sales than Google Analytics?

Sage and Magento says – $10k sales Google Analytics says – $15k sales from organic alone.

On data that analytics provides, I find it to be VERY accurate. Why would it ever register more in sales than the back end for fulfillment purposes? Is it possible that $5k plus in sales are being lost somehow? I would like to drive better results and make a bigger impact but this lack of trustworthy data is tough. Any insight from someone who's experienced this problem or similar to try troubleshooting again would be amazing.