I am referring to various control modules, wiring, and sensors. Some are internal to the transmission, some are external.

Whether or not you change the fluid is your decision. You can wait until the transmission fails completely, or you can change it. If you change it, it may improve the situation, or make it worse. You will know after you change the fluid, if you decide to change it.

One of the BMW techs on the board (Weasel, killcrap) may have a specific suggestion on further diagnostics using special tools.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue