What about that trick with the string while corking to let gas escape? Wet the string, drape it over the lip, cork and then draw the string out. I read this was a great way to relieve the pressure of the compressed air behind the cork. Still bulk aging my first real wine; others were Rieslings that I kegged. Maybe the air pressure + slippery corks were the problem?
Due to recent economic crisis, stock market crash, budget cuts, and the rising cost of everything including taxes: "The Light at the End of The Tunnel" has been turned off.