Hello @ll,
If you are using the GA traffic feature of LLTX, make sure that you don't use Carenado models as GA. Carenado has a copy protection mechanism, that makes it impossible to use their aircraft as AI. When they are created in the sim, they will shut down the engines of the users' own aircraft! LLTX tries to counteract this, but with complex airliner addons that usually fails.
Unfortunately I didn't realize that some of the default GA planes in P3D are from Carenado, and that they exhibit the same behavior.
1. There is a checkbox on the GA traffic settings dialog (click on the cogwheel next to "Add offline GA, helicopter and military traffic") that enables the automatic shutdown prevention
2. If that doesn't do the trick, please do this:
go to the Aircraft Model Database in LLTX (Button "Configure" below the AI package picture)
On that dialog, press "GA, Helicopters & Military", this opens yet another dialog
At the top, select "GA airplanes"
Remove all the "AC11 Commander" entries with right-click -> "Delete"
To be safe, I will remove the AC11 from the LLTX defaults in the next version.
Best regards