I know pretty much nothing about electronics, but I might have a bit of an insight into this. A friend of mine once had a piezoelectric butane lighter that didn't work properly. Just a valve problem, but of course I had to disassemble the whole thing to see what made it tick. When I put it back together, I inadvertently left out a small mica spacer that apparently shielded the case from the spark mechanism. Got a nasty bit of surprise when I tried to light the thing.
After I put the spacer back where it belonged, there was no problem.