Removing ORBX Global and landclass North America is a too radical measure. The altitude problem mostly lies in the given airport backgrounds (ABP). These are the green flat - often rectangular - areas where the airport is located in.
The new created airfield is not compatible in altitude with the existing ABP.
The ABP data are in:
\ Prepare 3D\Orbx\FTX_VECTOR\FTX_VEXTOR_APT\scenery
For example:
- ABP_U60.bgl
- ABP_ID76.bgl
- Etc
See what happens if you deactivate one of them.
After deleting this file you have to create a new airport background for the newly created airport using ADE. That can solve a lot of these problems.
Dieter