I just got one of these and had a bit of an issue with it because the connector pins 3 and 4 were isolated from each other. I guess you would probably discover that soon enough if you tried to ground the tip, but I had not gotten that far, instead it came to my attention as the standby feature was not working. That was because there no way on earth (so to speak) of the shake sensor pulling the processor shake input to ground.
Unlike the one shown in Porlock's photo (reply #80 here), mine shows no attempt to bridge those two pins (the tip of pin 4 has been nipped off, making it shorter than the other pins).
Later I found this in an Amazon review for a V3.1 one of these:
"... the specific one I got has some ugly and incomplete solder joints on pins 3 and 4 of the PCB board connection to the Iron connector.. As far as I have seen in a few EEVBlog posts and what I could spy from freezing frames on YouTube reviews, pin 3 and 4 are often bridged together, but as you can see in the pictures, mine appears to have a cold solder connection with an incomplete connection to pin 4. "
His photo shows one looking not that different to Porlock's one.
I'm darned if I can find where this has been mentioned here before, but then there are so many threads about these devices, and so little time...