Reading the logs, I can see it does okay up to
Inject Object at Airport: N853GT
Title: AIGAIM_Polar Air Cargo Boeing 747-8F
Airport: PANC
Aircraft
Throw Exception: 35
After this point, it always fails to add traffic.
Log_TrafficController.txt
Checking other airports, LAX will generate 747s. Could this be an issue with having no place to park the planes?
35 indicates exactly that... No many airports in MSFS can handle the big airplanes at the moment.