Small gap left during reassembly

One of the face buttons on my Pro Controller got gunked up and wouldn't press down the right way, so I decided to take it apart and clean it. Save for a stripped screw or two, I was able to get in, clean what was necessary, and keep everything intact. The trouble I'm running into is that the parts won't sit flush together when I try to reassemble the controller. I need to screw the faceplate and buttons back to the chassis that holds the motherboard and analog sticks, but the closest fit I can get leaves about a 2 mm gap between the faceplate and the glossy black plastic at the top. I remember having to unclip those two parts, so to speak, when I took it all apart, but I can't for the life of me figure out how to clip them back the right way. Any advice on how to maneuver everything?