I have heard of this on this, Several times, on BP. And if I remember correctly, it was around the 2 year mark. Personally, I have not experienced it. Maybe get hold of your nutrionist from your bariatric team for suggestions. I specifically remember at least one person coming back and mentioning the issue had resolved, but can't recall how.
On another note, it's great you have maintained your weight, relatively well. I never got down to my goal weight and have regained about 11 pounds! It's a real struggle to get it off.