Sorry about that...the bottom of the bottle is beginning to pucker outward slightly...so instead of being inverted towards the inside of the bottle, it's now flat to slightly rounded away from the inside of the bottle. Hope that makes more sense. It's a Dasani water bottle....so maybe that's why I'm having this issue. Should I think about either transferring it to a glass bottle or taking the cap off for a few seconds to relieve the pressure, squeeze the head space out again, and re-cap?