Wanted to get some opinions regarding my NX75, when I first purchased it about a month and a half ago the fire button had a distinctive click when pushing the button. Over time the click has disappeared and the fire button needs to be pressed in a specific way (push down and up) to actually "fire". It feels that as time goes on and I use the unit more and more the button gets worse and worse. Is this a known issue with the NX75? A friend of mine had the same issue, he eventually just stopped using his because the fire button only worked about 50% of the time.