it looks like the passenger door is recessed rather than being flush with the fuselage. With the plane under its own power I assume it's just landed or about to depart. So is there something about Tu134 doors that "unseat" on the ground??
I'd say it is probably because there is little or no differential pressure whilst the aircraft is on the ground. Perhaps the TU-134, or this example alone has a bulky door seal? I imagine the door would press out until it reaches the stops and become flush with the surrounding fuselage as differential pressure increases as altitude is gained.
JetMech split the back of his pants. He can feel the wind in his hair.