Your sliding mechanism which gives your wiper its unusual action is probably in need of lubrication.
Using your ignition switch stop the wiper at 45deg point where the blade is fully extended then unclip the plastic covers which cover the sliding mechanism , the one at the base of the wiper arm unclips easily but for the "turtle shell" you need to pull apart and up at 4 and 8 o'clock positions if you take the wiper arm as 12 o'clock, if it's stiff try pulling on just one side .
Clean the old grease off the 3 rods of the mechanism and regrease with silicone grease also run some oil into the point where the crank rod goes through the bottom casing.
Reassemble and hopefully problem solved,this should be done at every service but is not covered in service schedules.
Cheers,Geo.