Why does the cap unscrews will blending causing the liquid to leak out

I have same problem. I purchased new gaskets & new containers. The new gasket worked for a few months but problem has returned.

It’s resistance on the blades that is unscrewing the cap! If you’re mixing soft fruit and liquid only, this wont happen. An overloaded cup and/or hard items such as carrots Ice and the like is also problematic. cut the these things fine or crush them before placing in the cup and add water. Another thing to watch is those little lugs on the cap that insert into the slots that start the motor, push down only to pulse..if it pulls to the lock position on its own trouble usually ensues! Anyway this has been my experience, I hope this is of some assistance.

I have tried 2 different Bullets, they both leaked from the very start. Will purchase a different make.

I am having the same issue....(@Cannon I am highly educated in the sciences). My former Nutribullet did not do this. However my new Nutribullet Pro is doing this consistently. It does not matter how tight the cap is, it will always open. Like I said earlier, the Nutribullet NEVER did that regardless of the contents inside the cup. Is this a bad item or is the whole line flawed?

Simple solution. Just put a thin rubber band around the outside of the blade attachment so that when you push it into the mixer it is a bit tight and will not move easily when spinning.