Hi Matthias,
your logs show, that the meridian flip has been started and completed - but everything within 1 or 2 seconds. So obviously no pier side change has happened.
What does that mean? Well, it's at least no KStars bug, the problem is somewhere in your setup. Please check the following:
Are the time and location of KStars and mount in sync? There is a KStars / INDI option to sync KStars and mount. Is it enabled?