ERR 57 on 3720?

[Karl2]

Sunday morning and a ton of work to do. Wouldn't you know! My new 3720 (less than 40 hrs.) is giving me an ERR 57 message when I crank it. It says "ERR 57", then I think it reads "COA5E" or "COASE".

I think it's COAST but not always easy to make out the letters on that display

On mine it briefly appears when I adjust cruise control settings. I'm not sure the message is supposed to mean something on every model but I vaguely assumed it meant the tractor is in motion but not in gear either because the clutch is being held down or lever in neutral (on standard/PR models) or transmission lever is being held between gears or in neutral (hydro models) while in motion, thus "coasting".