help me stop launching bottles

I was doing a training ride by myself yesterday at race pace on basically an Olympic distance course.  The road was not particularly rough.  I have 2 gorilla cages behind the seat because everyone said they were the best cages for keeping bottles on the bike.  I was hammering a long, downhill section and my left bottle ejected wthout even hitting a bump.  I reached back to make sure my right bottle was there and it was still in the cage but it had ridden up to the point that it would have been lost in less than a mile.  I was using 2 cammelback podium ice bottles.  This is probably the 4th time in 2 months I have ejected the left bottle so I don't even use the rear system in group rides.  I know the cages are installed correctly.  I paid way too much for this system to get rid of it.  Anyone have any tricks to keeping the bottles in place?  Do I need to go with different bottles for some reason?

Also, I use the speedfill A2 between the bars for my main hydration and the rear bottles are for refills along the way.  This means I only need to take the rear bottles out a couple of times during a long race.  I was thinking a small amount of velcro or some sort of abrasive surface on the cage to help create friction with the bottle may help keep it in place but still allow me to pull the bottle out when needed.  Ideas?