I got a stickerless Lubix Zhanchi from my girlfriend last week. It's really really good, but the center caps keep popping off. It didn't happen too occasionally at first, but now it pops a lot, which is annoying when I'm doing solves. Really nothing happens except that the center caps pop. I've looked online for solutions, but most sources say to stick paper or tape in the center caps, which I don't think I'm too keen on. Any solution to this?