This sounds as if your automatic trip mechanism is hanging up, since it is occurring as the trip mechanism starts to engage.
Lift the turntable off the unit and take the arm and move it slowly toward the center of the record. Observe the trip mechanism as the arm moves toward center. You will see if there is any interference with motion of arm. The interference usually occurs near the center of turntable where the trip mechanism engages with the gear that drives the change cycle. Sometimes lubricant gets sticky or there is other mechanical interference.
I am not directly familiar with Marantz 6200, but I have a general familiarity with other automatic and semiautomatic units. A real Marantz guru might be able to point out your specific problem. You should move the arm VERY SLOWLY by hand toward center and observe the mechanism as arm moves. Everything should move VERY easily, and there should be no interference at all. If you can feel any interference with motion of arm, this will identify your problem.
And good luck from that interfering old guy,