I downloaded "Aerofly-Sim.de", first, the Predator model. Everything happened normally, except that when loading it in the PC, the Predator falls violently against the runway with an explosion sound (it sounds as if it fell several meters high with the consequent sound of the crash against the ground.) The fall is repeated every three seconds and the third fall, it is the last, from here on, it remains on the ground, and on its own wheels.
I loaded the next one (Piper Cub); it also crashes violently against the ground. This fall is repeated in about half the time of the previous one, and thus remains indefinitely falling violently against the ground.
I loaded a third plane, and the same sequence is repeated as that of the Piper Cub.
I had never seen this in any sim. Does anyone know this difficulty?