New springs installed but one does not operate smoothly

After having a spring break I carefully measured, remeasured and measured again to assure I obtained the 2 correct size springs for my 16'x7' double garage door. I installed the new springs successfully and the garage door functions as it is intended.  However, after about 3-4 seconds after the garage door starts to lift the left torsion spring makes a drastic adjustment and smacks down on the torsion bar making a loud banging sound. Beyond that the door continues to open successfully and there is no other oddity. Closing the door the issue does not occur.  

I've disassembled and reassembled the springs 3 times with the same result. Is there an adjustment I'm not doing?  What am I missing?

Thanks.