So, finally I found a computer with Windows and did a firmware upgrade. It changed several parameters (for example the sequencer stopped playing from a keyboard), but I could correct the unwanted changes, and finally after the upgrade, the CC 102 is working, so probably it was a firmware bug. Sometimes, when I turn MicroBrute on, the local keyboard is switched off, but after a restart or CC 122 it works, so I can live with it. Otherwise it's a great synth, and with a simple external effect processor it sounds like a very expensive vintage instrument!