You did all the usual checks with A6 problems, time to contact BG CS for a replacement. There is a contact information on page 1.
[EDIT]
From: Code now public! BLF A6 FET+7135 Light. Short 18350 tubes and Unanodized Lights Available
8/31/15:
For those that are having issues with their light, you can use this email address: heyanqing1@banggood.com
That is directly to Neal’s assistant. They will help us get any problems ironed out.