Tried that last night after the SIM snake oil didn't work. Both factory restore without restoring my backup, and a factory restore followed by restoring my backup. Neither helped. Same issue... bars drop when I touch the sensitive spot on the lower left side of the band.
Something interesting, which I don't know if anyone has tried or documented, is that the same signal droppage occurs if you bridge that little gap with a piece of conductive material (I used a paperclip held in place by scotch tape). Without even touching the phone with my hand, the signal bars dropped as expected.