Astreas are the worst for flipping over. I bought 25 a couple months ago and put them all in my tank. I spent the next week flipping them back over and I'm still pulling the occasional snail off the intake of my PH
I still have 15 or so left. Pleanty of shells on the bottom for my hermits now
I finally gave up on flipping them over, I figured they were the "stupid" ones. I guess you could call it natural selection. Thank you Darwin.