Some keys I have to press hard for it to respond.

I own a 2012 27-inch iMac, I was using a Logitech Keyboard since I purchased it, but just recently took the wireless keyboard that came with it out of the box, so it's been in storage in the iMac box for almost 2 years.

I popped some fresh batteries in it and come to learn that some of the keys I have to press with force for it to respond. Is this something just from being in storage for so long or is it because it's broken?

I tried swapping batteries, blowing some compressed air under the keys, but still they require a very forceful press for it to respond.