i have had the same problem with my SB. I plan on calling altsmoke about it when i can. This is by no means a bash towards altsmoke i LOVE my SB. my problem first started when the oring in my 510 connector split. took me a few days to figure out what happened (was allowing the connector to short out and making the batterys HOT). yes i know its not recomended but i stack rcr123a's. anyways new oring and some heatshink on the solder connection and i was good to go.
Few months later i was having the same problem you were having. I noticed that if i pressed the button and slid my finger back and forth across the button i could get it to fire. after about a week it started working correctly again......long story short i found out that my
tank was leaking past the sealed 510 connector and
juice was building up inside my switch. the gunk wouldnt allow enough current to fire the carto.
so I order a new switch and got it replaced today. this time i used a little silicone to seal the switch. that way if it ever leaks again, it wont gunk it up. I also ordered a new 510 connector.
This is the only problem i have had with my SB. hopefully this will give some people an idea of what is going on if they have a similar problem.