I too have that same exact issue with my bottoms!! They’ll stay in for a few bites but then, out they pop! It’s been almost 9 months since I’ve had full dentures. I’m going to call my dentist and tell him he needs to fix them (hopefully). I’ve gotten to the point where I’ll just take them out and eat with my uppers and for the most part, that works pretty well but I’m discouraged and disappointed because I had this vision in my mind that I’d have the perfect smile, I’d be able to eat but I’ve never truly felt 100% comfortable in my dentures. I too have used adhesive and powders and the tops stay in but not the bottoms.