[Austin W Hogan]

If the floorplate has warped, a good hit in the right spot might take care of it. The problem is to know the right spot and the right hammer.
The floorplate probably began to work while still in place. Releasing it during dis assembly let it come to a new equilibrium. Try this; mark the entire edge of the floor plate with magic marker if you do not have layout blue. Place the floorplate in the frame and give it a light tap. Remove the floorplate and look for lost color; those are the tight spots.
Cover the back of the floor plate with a thin coat of grease. Insert the floorplate and tap. The grease will adhere to spots where the floorplate touches.
Have you checked the floorplate with a good, hard straight edge? That should verify if warpage has occurred; metal parts also grow when blued, or when corrosion begins.

Best, Austin