Hi,
Server: EU Megaserver, live
When two or more people cast Wall of Frost (any morph) at the exact same time, a random person around them (may include casters) will crash. We were able to replicate the crash in 100% of experimental cases. Sometimes casters crash, sometimes people around them. The only condition is that the cast of both (or more casters) must perfectly match.
After removing frost blockades from our trial group, we were experiencing significantly less crashes than usual. Not all crashes are caused by Wall of Frost, but at least you'll avoid the most frequent ones this way.
I suspect this happens due to graphic extensive frost shield animation but I'll leave this to ZoS to investigate.
Thank you for your time and hope for quick fix.