Definitely lube the sunroof rails. Cable will be more of a problem, I'd avoid that unless forced to.

Manual operation is pretty stiff.

Closed location is by microswitch, so it's possible that something has gotten out of alighment in the motor itself, too. Does it just click or does it hum? If it hums or buzzes with the roof somewhere besides closed and flush, its dragging too much and the motor is slipping on the clutch. If it just clicks, something is wrong with the microswitch control inside the motor, most likely.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!