Are you buying them from a coop or making them yourself? If you make them of course you can control all the variables, I'm not questioning your ability but if you are making them your straining the bud from the butter right? Maybe your using too much butter or your stomach just doesn't want to digest herb, I have a friend that can't eat meddles, he once missed 2 days of college after digesting some, maybe it's just not for everyone.
If you're making your own meddles, might I suggest making glycerine tincture instead? Since I found tincture I RARELY make butter or cook with herb, I typically mix it in with my morning coffee or at night with tea, it can also be digested under the tongue.