That makes sense, and I appreciate the reply. I'm only using the 750 or 530 versions, for reference.
However, I believe the problem is something like not having all the AIRAC data properly pushed to the sim (I don't know the proper terminology for this, so...)
The reason I say this is because I ran the same type of LPV RNAVs into several different locations and found no issues, went back to the airports near my home, and found issues... tried to reset the plan while in the plane, tried a simple ESC, RESTART the flight -- and suddenly it works as intended! So it seems as if some approaches simply don't populate the sim/GNSS system properly on start up, and sometimes they do. I suppose this may, or may not be something that you have any control over.