Yes ,its a common issue on the 60 70 and 80 series
Have you cleaned the guides deep inside the door.They get gummed up and cause extra friction.
If you spray some water on the guides and they begin to move up and down easily ,you will know its the problem.
The low power issue is usually bad contacts at the controls on the drivers door and the offending door.
Usually the door furthest from the drivers door is the worst,in your case the rear LH door.
Its nearly always a combo of dirty guides and bad contacts
Shoot straight ya bastards and dont make a bloody mess of it.
Breaker Morant at his execution
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