Slight issue with Technics SL5

[synsei]

Occasionally the SL5's arm lifts and returns to its park position when it reaches the half way position on the last track of a side, any ideas how I can rectify this please? :)

[DSJR]

In the first instance, check the arm carriage linkage and drive belts if any, which may give slightly jerky movement to the arm-pivot assembly, 'tripping' the return circuits.

The above may be a load of bobbins, but I seem to remember these parallel trackers needing attention now they're thirty five years old..