Besides the lubing of the spring, which is the most important part of the wiper arm recondition, there's also another less talked about but also possible cause of the wiper malfunction.

Sometimes the wiper arm has been taken off and reinstalled incorrectly, making the wiper blade contact surface with the glass less than ideal.

Take off the wiper arm by popping off the cover, use a 1/4" ratchet with a 13mm socket to remove the 13mm nut. Pull the arm at the base straight up with some force to remove the arm.

Clean up and lub the spring as needed.

Here's the important part:

Install the arm by inserting into the screw with the tip of the arm aiming at the ground. This allows a very good fit of the entire arm to the base of the motor and eventually flush with the surface of the glass.

While holding the arm down with some force, gently bring the tip of the arm to the edge of the rear glass, making the arm and the wiper blade as horizontal as you can to the edge of the glass.

Now tighten the 13mm nut holding the arm to the base and put back the cover.

Doing both the spring lube and the arm re-position brought my wiper back to 100% functionality!

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2003 X5 4.6is Estoril Blue, acquired March 2018
2013 128i M Sport 6 MT Space Grey daily driver
2010 535xi 6 MT Barbera Red