... to Shane Bester for finding a repeatable testcase for the bug report #14829, where I asked for help early this morning. The bug has now been acknowledged and it is likely that the bug will be fixed soon :-).
This showed me once more how great this Community works. If there is a problem that I can't solve myself, it really works to ask for help and get some assistance. That's one of the points that makes MySQL more attractive than many other products.