No wiper is going to work correctly if the wiper blade/arm is u/s and the blade should also be set up correctly in relation to the screen:
1. Switch on the ignition.
2. Switch on the wipers.
3. Stop the wipers (by switching off the ignition), just before they get to the end of their vertical position.
4. Pull the arm away from the screen and then very gently , lower it back on.
The "rubber" blade should now have it's edge touching the screen and be at 90 degrees to it. This can be seen clearly from inside the car.
5. If the "rubber" blade is tilting either way from the 90 degrees, the flat metal part of the wiper arm needs to be twisted gently to bring it back to vertical. Keep repeating 4., until 5. is achieved.
Do not try and twist the arm by using the wiper blade. If using pliers or "grips", ensure the paint on the flat part of the arm is not damaged, by using something like cardboard (cloth won't work) between the jaws and the arm.
If you cannot achieve 5., either the insert/blade is u/s, or the arm itself is putting too much pressure on the blade.