Do you have a locking fuel cap?
I spent a LOT of time trying to figure out why my NX was getting water in its fuel. I checked my tank, and found none; checked my Kubota, found none; checked my Polaris (diesel), found one; checked my generator, found none. Was dealing with some other issues with my dealer and just kind of tossed out that I hated their cheap locking fuel cap (chintzy as heck), only to have them send me a new one; the new one was much better than the original. As is typical of my dealer, there's never a backstory on anything (I'm always left guessing as to what the actual fix was, or why). Since then I've had ZERO water in fuel issues. My tractor was purchased late 2016. Got the replacement fuel cap 2018?