I also had this issue on a dedicated server I've set up this morning. I don't know if this was happening prior to 1.70 as I wasn't running a server then. I have some basic scripts in the mission and it has a bunch of mods... I can try running a vanilla server and see what happens tomorrow? Local network. Dedicated Server and Client on one box and another client on a separate box.
NetServer: trying to send too large non-guaranteed message (1360 bytes long, max 1348 allowed)
Message not sent - error 0, message ID = ffffffff, to 1875484644 (jerky)