|First of all. is it a Laptop or a Desktop ?|
whatever it may be, Its a problem with that particular Key. Check if there's dust accumulation underneath the Key. ( If its a laptop, it depends on what kind of keyboard it has. Some like Vaio and Mac have a different type that cannot be removed easily. Others like HP and Dell are quite easy). You could actually try removing that particular key alone and clean or blow off the dust with a blower. Sometimes due to wear and tear the silicone bud might have jammed or disintegrated and stuck inside. Let me know whats the status. I can assure you that its not a software issue. Thanks.