Older age maybe?
Maybe try Smart Gut Ultra and see if it has any difference on him. I’m not sure about the money back, but all of the people that do the smartpak stuff seem nice and willing to help you out so maybe get in touch with one of them and tell them your problem and ask what they would recommend.
Good luck and I hope you get rid of the problem!
~If you come at it having only 15 minuets it will take all day... If you come at it having all day it will take you 15 minuets~