The light on mine seems a bit dodgy as well. Wouldn't turn on at first, but I pressed hard on the battery cover incase it wasn't making contact and then it worked fine. I then took the head sculpt off so I can fit the bandolier, then put the headsculpt back on and the light went dodgy again. Now to turn it on, i just tilt the head slightly, lol. I know it has something to do with the contact again, but I can't be bothered 'fixing' it, since it's just a gimmick anyway. It looks cool, but only stays on for a few seconds, and I'll probably take out the batteries in case they leak.
By the way, if you have a dodgy leg, check to see if one is shorter than the other, or if you have any loose joints. Mine had a loose ankle and wouldn't stand up on it's own. The leg was also slightly longer than the other. Found that the ankle peg wasn't in the boot hole all the way, but also I think the hole was a bit big, so I wrapped the ankle peg with a bit of electrical tape and pushed the peg all the way into the boot. Stands up no problem now. Also make sure that the ratchet joints are fully locked into place, including the ankles.