Didn't observe till now, but my CM Devastator 3 KB does the same if pressed from sides of the KB key. Don't think its an issue. Although this doesn't happen on my laptop KB but both have kind of different mechanisms & travel distance.
I mean, I don't feel a lot of difference in actuation force required, but yes pressing from sides requires a bit more force. After checking more, it seems just some keys show that behaviour a bit noticeably, not all. Might be dust, not sure but naturally I press at centre of keys, so never observed before today.