I have removed/replaced something on the order of 200+ sideplates on all manner of hand ejectors and top breaks over the past 60+ years with nary a problem----and nary a sign of any sort they've been off and on---and never involving a hammer of any sort!!
And when you're pressing the sideplate into place with your thumbs/fingers, and it stops before it should-----something ain't right. That's a clue telling you to remove it, and start over. With a later hand ejector, the something that ain't right is the hammer block needs some attention---up, down, or sideways. You're working with an inanimate and precision object. It'll do exactly what it's supposed to do when it's right. There's NEVER going to be anything wrong you can fix with a hammer----guarandamnteed!! Pretty much the only use for a hammer is to use the handle to get the sideplate OFF-----if the handle is made out of wood----or plastic---God forbid you should have a hammer with a plastic handle.
And when that sideplate is in place, and even all around, but not all the way down, that's pretty much to be expected every now and then----even often. It'll be all the way down after you run the screws in------with no extra effort to speak of.
Ralph Tremaine