I had this issue with my under eye. It was just the outer corner that the damn concealer would not blend into the foundation not matter how long/hard I tried. And then it would get all patchy and when I set it the texture was even more emphasized. It was a mess. I was using Revlon concealer and I actually posted about it on here and someone mentioned that the formula is really thick. I switched to the NYX HD concealer and its so much better. I also barely put any foundation on my under eyes so the concealer isn't caked on and doesn't break up. Maybe try a new product? Less product? Also are you using a primer and/or a moisturizer? Your makeup will stay better if it can latch onto a tacky, smooth surface.