Ok, I figured it out. Just so you guys know, when building the Ortho4XP tile (+36-116), users need select "false" for "high_zl_airports" under "DSF/Imagery" in the Ortho4XP settings. If they do not do this, then you will automatically end up with mixed ZLs.

I followed the instructions for integrating Ortho4XP into this scenery and I continue to get this error.

Any ideas?