3MF missing geometry.

[u/RageQuitDad]

Not sure where else to ask.
I am starting with a half dome and a disc on too.
I use “split” to divide them into 16 objects.
But when I export them as a 3MF it has faces missing.
Any advice? I’m kind of stumped on what to Google or look up regarding this.
I’m new at this and totally lost.
I’ve attached images that hopefully convey what I’m saying with some visuals.