M30 mouse side button problem

The side button nearest the front of the mouse seems to be a lot easier to press and activate than the one behind it. My first M30 which had a scroll wheel problem didn't suffer from the button issue so when I received my second mouse I thought it was a fault. However the third mouse exhibits the same problem.

 

Is it supposed to be like this?

 

Please respond soon as I'd still like to get this swapped out by my retailer if it is a problem.

 

Thanks

Had to get a refund. I think I've spent more in fuel trips to swap them out than the actual mouse cost, so I've cut my losses.