My rear wiper has recently been groaning and giving up after a couple of sweeps but always seemed to come back to life later.
I had seen a thread with photos of where the cover was removed and the gears etc greased but cant find it now.
Mine was a bit dry but after an initial greasing and refit then a more thorough strip down and lube the motor was still labouring when the blade was in contact with the screen.
I bit the bullet and removed the motor assembly and worm drive then removed the rear cap and lubricated both ends of the motor shaft, reassembled, bench tested with 12v direct to motor and its as good as new now.
In hindsight the motor probably does not need to be removed, the shaft behind the worm drive can be lubricated from inside the gear case leaving just the motor end cap to be removed, unusually the brushes are at the output end so its safe to remove the end cover and nothing will go flying about, the bushing was dry and causing the seizing, another possibility is grease getting onto the circular tracks for the self park mecahnism creating resistance so its worth cleaning them up and the 2 contacts.
The circuit board can be removed allowing direct access to the motor terminals for bench testing.
Had I not wasted time on the first 2 removals & refits then the whole job would only have taken 20-30 minutes, definitely worth doing before shelling out £80 or so for a new or second hand motor.