I just purchased a set of Aristocraft's 29107 powered trucks for their Sierra passenger cars. On both trucks, the solder point connecting the black wire to the axle receptacle is broken. So whenever some weight is applied to a truck, the black wire loses contact and power is lost. The solder for the red wire on the other side of the truck is fine. The fact that both trucks have the exact same problem is a little disconcerting. This should be a fairly simple fix, but has anyone else had this problem? I was looking to get some more to replace the trucks on some LGB passenger cars so they could have track-powered lights. Is this a common problem or did I just have bad luck?