I have a similar issue with this wheel. I can not shift gears up when on a straight stretch of the track.
If i turn the wheel, it changes gears normally.
I also believe this is a faulty contact inside the wheel somewhere.
Ive also noticed that the manetino lights are off when I am on straight, which is another indicator of bad contact of the wiring inside.
Have you had a chance to get it fixed?
What did you do?
I am thinking of opening the wheel and trying to fix it myself.
Have you seen any video or pics on this wheel being opened for fixing?
Best,