It will be one of the carb sources not agreeing with you
Quinoa, Oat Bran, and Buckwheat are what comes to mind. Do you ever try consuming these on a regular basis in your diet and see how you respond to them? Some people can't handle different carb sources and get digestion issues which would be a reason why you don't handle the ingredient profile well.
If you have not tried cooking or eating those on a regular basis, try substituting them in and you will find the culprit through trial and error. I have been through multiple tubs with no issues, but I also can digest all 3 sources no problem if I use oat bran, buckwheat to cook with, or eat quinoa as a carb source in a meal.