Metal shavings and stuck starter button
Since my tachometer still was not working, I had to fix it before more testing could be done.
So I dismantled the faceplate (2 screws and some wiggling later it was off) and disconnected and reconnected the cable from the tire sensor and the main connector for the electronic display.
I also removed the sensor and noticed some fine metallic slivers sticking to the apparently magnetic sensor.
After wiping of the metal slivers and remounting I took the Spidermax to see if my work was successful.
The effort was successful but now every time I needed to break the electric starter engaged.
WHAT NOW??? I was not even near the @#& starter button.
OK you bastard, lets see if a general amnesia will cure you. So I pulled the fuses for 1 minute and my bike remembered that she was a nice person and everything was all right again.
Now I know why the fuse box is so easily reachable.
One day later:
The problem that the starter engages when I brake is back. Pulling the bottom fuse ECU battery for 30 seconds and wiggling the starter switch solved the problem again. If the problem comes back I will check if the starter button might be stuck.
Update another day later:
No problem starting and pressing the brake thereafter, so I wanted to check my starter button theory. Pressed the button a bit off center and I noticed it did not pop all the way out. Pressing the brake engaged the starter again.
So when I am in the mood I will see if the button needs some cleaning or just a bit WD40.
... WD40 did the trick.