I had been using regular vanilla flavored for a few weeks and was having major stomach/gas issues. It was becoming a real problem. I scoured the forum and saw a couple mentions that switching to unflavored/unsweetened worked for them.
I’m happy to report that this solved the issue. I think the sucralose / sweetener was just not vibing with me at all. I add cinnamon to it and it tastes just like Life Cereal. I’m a fan!
If you are having persistent issues, try switching to UU and see if that works for you before you give up.