What about swapping throttle bodies from one of your other 570s?
What is your elevation? I'm 4000-4500 and don't have your issue. But also I'm not in an area with the Winter blend ethanol fuel either.it’s no theory, it’s proven fact around here that you don’t run high ethanol fuel in the winter time even my local dealer has been pushing that fact as well.
Same here with the exception of the annual FI cleaner. I did run some Seafoam through it once and it wouldn't hurt to do it again. I've never had a starting or fuel problem but on three wide spread occasions I've had it shut down when cold after start up but after restarting no more issues.Have run premium, non-ethanol with stabil for 5 years in my 2017 900 XP EPS and it starts and runs great in any weather. It has been down to -17 in years past and always fired right up. I also run fuel injector cleaner through it once a year. Just a suggestion.