Interesting I've experienced this too though interestingly it is way more noticeable for me with beyond than impossible. I get a weird after taste for hours and my stomach feels off. Not bad enough to never eat again but noticeable enough that I tend to avoid beyond in particular now. Some people have suggested it is so close to meat that your stomach just isn't used to it but I'm pescatarian and eat fish fairly regularly so I doubt it is that simple.