You're probably "hitting" the ball on the upswing, which means your thumb is not exiting at the bottom of the swing. One thing you have to do (I had similar problem) is to bend your knee enough so that your hand is much closer to the floor. The second thing is you need to learn to trust your hand release.

A side consideration is a question about how well your thumb actually fits and is "knuckling" involved. You thumb should be almost flat in the ball and the thumb hole should be tight enough to allow you to hold onto the ball with minimal effort. The thumb should never be so loose that you knuckle it to hold onto the ball. Because this is not mentioned in your problem statement, I have no idea how well the ball fits or [i[seems to fit[/i]. Maybe you should get a good coach to help you through this concern and investigate the potential causes.

How much lateral pitch in thumb hole?  If you have alot of under palm pitch this would cause your thumb to exit later combined with any squeezing would result in loft.  Maybe pitch your thumb more away from palm with a snug fit and no muscling/squeezing would help?

900dj is thinking exactly what I am. Changing the lateral could assist in feeding the ball into the lane. Couple that with solid footwork and you should have a solid in which to begin teaching yourself your new release technique.
 

This may not help you because you have late timing.  What I try to do is imagine that you are a pilot and want to land your plane (ball) onto the runway (lane).  Most airports use a 3 degree glide angle, so the approach is a very gradual drop in altitude not a sudden drop where the passengers will lose their lunch. 

Start with keeping the knees flexed, not locked.  Have a bit of tilt at the waist and try to get lower with each step of your approach.

Happy landings.

check your pitch on thumb or enlarge the hole for earlier release.