the bulb in my ones matrix blew after two days (admittedly the bot hardly left my hands for the first day, i'd have taken it to bed with me if my fiancee had let me!!!!!)
yeah the fix is pritty easy, just put some super glue on an ear bud/swab and put it round the black hoop in the hip, you could just drop the glue in but if it needs to be opened up again it could glue the whole hip together
i found the problem to be the hoop should have clips on the shorter teeth but the mould must have been warn out, if you pull both legs out you can see the clips warn down