The shifter in my 2008 135i no longer upshifts when in manual. Fully automatic works fine. The paddle shifters work fine in both directions. The shifter works fine when downshifting. So, it's clearly not a mechanical problem. I assume the shifter uses microswitches of some sort and that the upshift switch has gone bad or become disconnected. Does anyone have any idea how to go about tackling this issue? Is the first step to take apart the shifter? Are the switches located there? Has this been a problem you've seen before? Any tips or ideas? Thanks so much.