The off angle at the center position was small. With the arm at the center, I could insert a piece of typical copy paper (Zerox Multipurpose 4024) a little through the gap between the arm and the glass on the left side.
After the twist correction, I could not insert the piece of paper on either side.
The wiper did not squeak on dry glass.

Yesterday, it rained. So I tested the wiper. Before the twist correction, the wiper squeaked at the right end position. But yesterday (after the twist correction), it was squeaking at both left and right end positions.

I brought the Bosch blade home, cleaned it with Meguiars Heavy Duty Carpet Cleaner, rinsed it, and applied TurtleWax Platinum Series Ultra Shine Protectant on it. I heard I should not use vinyl/rubber protectant on wiper blade, but I did. I let it penetrate for 5 minutes and wiped off excess with napkin, wiped the edge (where the rubber contacts the glass) with dry napkin several times to wear out the protectant residue.

I went out and tested in the rain. Streak due to the protectant was soon gone. I tested for about ten minutes at intermittant wiping setting. There was no sqeak anymore, and the wiping quality was the same as it was before putting protectant: haze on the swept area evaporated out in a blink (0.1 ~ 0.3 seconds? I did not measure, but the duration of the haze looked the same as before putting the protectant).

I will post when the squeak comes back.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.