Peter is, as always, right. Without a cartridge the arm will float free to some extent and may swing a bit to the side when "playing" and it can sometimes cause the tracking mechanism to start driving the carriage towards the left until the end-of-record point is reached, it will then "lift" and return to stop.
Beogram 4000,4002,4004 and 6000 makes a clear audible click sound when releasing (lowering) the arm. This click is directly related to the lowering mechanism and is a sign that a record has been sensed and the arm is to be lowered.
The others (6006, 8000, 8002 etc.) are different, the tiny click that can be heard comes when the arm has been lowered all the way and the muting relay activates, allowing sound through. The click is from the relay, not from the lowering mech.
Martin