Topic says it..
Timecode frequency is set to “never”
Markers will either display as timecode-style hitpoints or rehearsal markers, depending on whether the marker track has a linear or musical timebase, so switch to musical mode.
Got it!
Thank’s 
Ok, that’s a solution.
But I always wonder why there are so many automatic dependencies.
It should just be possible to manually adjust the display of the markers.
It could be that I want a linear time base, but still don’t want timecode in the markers.