The first thing that comes to mind is the deck leveling. Since it's a newer model, you can easily find the user manual and see what are the steps to check and fine tune the leveling.
If your 2016 X350 is cutting unevenly even with sharp blades, check deck level, tire pressure, and blade alignment. Also inspect for bent spindles or buildup under the deck, it can really mess with cuts
yep, @DrivingTheScrew is right, but If you've already checked the deck, the next thing to do is to check your tire pressure!
Even a small difference of a few PSI between the tires can cause one side of the deck to sit lower than the other. Look at the sticker on your tractor or in the manual for the recommended pressure, and make sure all four tires are inflated to spec. It's a quick and easy thing to check that can solve the problem instantly
I had the same issue with my X350 last season and it drove me nuts. Don't forget to check the spindles and deck hangers for wear. Sometimes it's not what you see at first glance.