Deep Packet Inspection and Wikipedia

Bit of a weird one..

Over the last couple of days we've been experiencing temporary outages on our Fortigate 60D firewalls (running 5.2.3) when trying to browse wikipedia (specifically https://en.wikipedia.org).

After some testing today it appears that internet connectivity drops when attempting to connect to Wikipedia from inside the LAN with a deep packet inspection profile enabled. Wikipedia fails to load and all internet connectivity disappears for a couple of minutes. This behaviour is reproducible simply by browsing to any Wikipedia article again.

Adding an exemption for *.wikipedia.org to the SSL inspection profile seems to have resolved this (I'm still testing) however I'm curious as to why this behaviour is occurring.

Has anyone experienced this type of behaviour with Wikipedia (or any other site)?