Fortinet 60D ERR_EMPTY_RESPONSE

I have a situation that I can not figure out. I have a Fortinet 60D with no UTM no website filter and I think ssl packet inspection is turned off. Dual wan fail over VZ primary on WAN1 comcast secondary on WAN2 using static route administrative distance with about 50 comps behind it, about 15-20 in use at 1 time.

We have 1 propriety website hosted on a dedicated server and we get ERR_EMPTY_RESPONSE and or it just hangs with a spinning circle. The datacenter said this is something on our end. This is the only website that does this and it's their propeitry CRM application. Is there anything I can look at to see why this is doing this. It does not do it on any other ISP. I've tested at my house with a fortinet, at my office, other clients sites. It's just this 1 site this website seems to get hung up on something with the nat forward or SSL packet inspection which I beleive I've disabled. There are no UTM or proection rules on the internet policy