Movement spacer issues

Hello all,

I'm in the process of doing my first ever build and I've come across an issue I was hoping you legends can help me out with .

I have a 43mm Explorer 2 style case and using an nh34 movement. Because I'm using the 43mm case and not the 40mm, the case came with a plastic movement spacer (holder), which prevents the smaller movement from moving around in the case.

The problem I'm having is when I screw in the case back the internals of the watch (specifically the pinion shaft) get pressed against the crystal which stops the second hand from moving.

Based on my diagnostic of what's going on, it seems like the movement spacer is too thick but I could be wrong (I am a rookie).

Does anyone have experience with this or know of a fix that doesn't require sanding down the movement holder?

Thanks in advance!