Had the same issue on mine using (at first) Bosch aero twin (?) but the drivers side shuddering on the way up, fitted a new set of OE Denso blades and the same issue.
Had a close look and on mine and when parked (the wipers) I just put a little bit of upward pressure on the nearside blade and you can see it flip the blade over for the up sweep.
As I tried the same on the drivers side it did not and stayed flipped over in its down wipe position, removed the blade and gripped the wiper arm at the flat section that holds the blade with a large pair of pipe grips.
This I protected with a strong strip of cardboard to avoid any scratches to the arm and gave it a little twist by twisting anti clock in my case and then checking, sorted it first time and now quite as when parked they both now flip over on demand for the up sweep.
Hope that makes sense, if not I will get some pictures up.