I installed Xplane 11 with it's default scenery... Saint Hubert CYHU has it's buildings (about 25 miles away from Montreal CYUL)
I install the CA-A files then the CA-B mesh - With the CA-B-CYUL_Montreal_Mesh folder, the buildings disappear.
Erase said folder and buildings reappear.
This does NOT happen with other sceneries such as C Montreal.
If the mesh is so complicated, it's affecting regions miles away from CYUL. Guess I'll have to investigate other nearby airports to see if it happens there as well.