copy this from bimmerfest for "BMW Tech" person & it worked for me after I showed this to my dealership:
Typically, wiper inserts lasts up to a year before they begin to streak/skip/and chatter across the windshield when used. Your problem appears to be abnormal,therefore I would suggest visiting your local dealer to perform the procedure I am about to post with illustrations. It may appear to be over engineered or simply ridiculous, I agree that a pair of channel locks or regular pliers and a watchful eye could do the job. Precision is key, hence the use of these special tools. The end result is therefore effective if done correctly. Guesstimation versus precision, guess which one proves to be precise by definition. Skills or experience of the technician following the procedure won't matter much. If one can see, read (alpa-numeric/english language/sesame street contents), walk upright, with 2 hands/eyes/and not a zombie....your chances of getting this fixed........90 precent.
The 10 percent goes towards the possibility of you ending up with a brand new windshield because the tool fell on top of it or something of that nature.
Follow along with the picture and see for yourself.
----Wiping quality is increased if the approach angle of the windscreen wiper arms is precisely adjusted.
-----Adjusting dimensions of wiper arms:
Reference points (A,B) are the mountings of the wiper blades on the wiper arms to the sealing lip (1) of the cowl panel.
Contact angle (C) is the angle between wiper blade centre plane (2) and windscreen.
------Remove wiper blade (1) from wiper arm (2).
Pin (3) is locator for special tool.
-------Slide special tool 61 6 100 onto pin (1).
Place special tool 61 6 100 on windscreen (2) and read off value in degrees on scale.
LHD vehicles are covered by the scale range of 0 to -10
-----If the specified number in degrees is not correct, the wiper arm (1) must be bent with the special tool 61 6 110 at the point shown.
Refer to attached pic for the referenced information
A/B = Distance between windscreen wiper blade (2) and trim panel on cowl panel (1)
Note: Measurement is taken at the height of the locators (3) for the windscreen wiper arms
C= Contact angle between wiper blade centre plane and windscreen
When adjusting with special tool 61 6 100, set the scale value in accordance with the following table.
For RHD cars, change the preceding sign of the scale values.
• LHD cars, scale range 0 to -10
• RHD cars, scale range 0 to +10
Contact angle (C) on windscreen wiper arm for E90/91/92/93
86.7 degrees on the passengers side
86 degrees on the drivers side
---plus or minus 1 degree on both so I would probably place it dead on at 86 degrees
Scale value (LHD) on special tool
-3 (negative/minus) on the passengers side
-4 (negative/minus) on the drivers side
Adjustment dimension (A , B) on windscreen wiper arm
88 degrees for passengers side on E90 and E91
75 degrees for passengers side on E92 and E93
----plus or minus 3 degrees
95 degrees for the drivers side on E90/91
84 degrees for the drivers side on E92/93
----plus or minus 3 degrees