Glycine Compressor Snap Case Back - SUPER Tight - What am I missing?

Ebay purchase of a basket case Compressor in parts/disassembled. Everything went well until assembly. The press in case back is super tight to the point where I don't want to go any further before asking. I've owned the Airman pumpkin with the same back and don't remember this kind of pressure without success. Right now, I would say it's halfway down and feels like I hit a wall. There is a clip of some sort on the inside inner ring that I thought was more related to the movement holder. Maybe there should be some orientation of the clip before?
I'm using the standard screw type presses with different sets of poly / aluminum adapters to press on the outside of the case / case back.
Anyway, I have this thing half down and wondering if I have had a brain fart. There is play inside so it still needs to go in a little further. Suggestions are greatly appreciated. BTW, the stainless crystal trim piece was super tight, too.

There is often a cut out in the lip of the back for the winding stem, so make sure that if that is present it is aligned with the crown. Without seeing the inside that’s all I’ve got…

Here are a few more pics. Case back is smooth with a deep groove. Nothing keyed for a stem. There is a retainer clip on the inside lip similar idea to the clips that hold on bezels. Bumped out in 6 places. I suppose I need to get beyond these with the lip on the case back. I put more pressure on the back than I have ever done before. Thinking about a dab of silicon grease on the points that would come in contact with the lip of the case back and try again.

Yes, some grease might help.

Got it! A little grease did the trick. Loudest pop I've ever heard from a watch. Worried that I might have jarred the hands loose. All good.