Are you sure the server is able to see the clients FOV settings? I never saw any code nor any packet for that.
//EDIT: Also the packet sets the walk speed, not the FOV. The client maps speed to FOV. Do you really think it would be an option to reduce walk speed just to fix the FOV? What if the client has max. FOV? Then the packet couldn't modify the speed at all.
Yes, I also think this is the cause.
The problem with this is that Packet202Abilities is able to do it, no matter if vanilla uses it for that or not. Mojang coded this for a reason. Also as it's a client bug you can't tell it's bukkits fault.
Actually I have to correct this, it only happens if the FOV setted in the client + the FOV from the packet is higher then the maximum FOV. Sorry for not being clear in the report.
Alright. Have a nice time getting the same report again when official API is released then just because you decided to not inform Mojang coders soon enough... 😛