Faulty brake switch fix: remove the brake switch by unplugging the connector and rotating it 90 degrees. Take it out to your workbench and disassemble (very easy, just some locking pins on both sides). The spring inside will pop the housing out. Clean thoroughly and adjust clearances. Reassemble and measure with a multimeter, one circuit should be interrupted while the other one is connected at the same time between the pins. It's a very simple device.
So no more warning light and no more error codes, success!

The pressure is regulater correctly between 95 and 85 bar (dropping slowly because some air is in the system, then re-pressurized by the system back to 95 bar).
Well, not entirely. I have been trying to bleed the Viscomatic system after replacing some of the copper gaskets by the accumulator using the F/L Tester and the "Ölablassung" (as written on the tester) or "Reinigung Öl" (as written in the module manual). Keeping the engine revs around 2000, the test runs correctly for about 5 minutes, keeping the pressure around 100 bar. Then unfortunately the test stops with a message "Bewegung Kolben falsch", meaning "bad piston movement" I guess. The test stops and no error code is saved ("no errors found"), the warning light does not go on.
I have checked the resistance of the piston sensor on the coupling and registered above 1k Ohm between two of the pins and around 2k Ohm on the third pair, which according to some old post by Wilco should be correct.
What does this mean? What do I look for? What should I check?
