I guess it's not really a problem. It's just something I noticed when playing with it. If I hold the phone in one hand with my thumb positioned on the power button then slightly rock my thumb up and down the button has a little play in it. I'm guessing it's just a trade off from using ceramics. I wouldn't label it as a fault though.
can't seem to replicate it but my oppo does that.. never found it to be a problem tho! rooted already.. eh.. lasted 30mins