you may be on to something and have found a bug. I reproduced this and it does as you say in the step editor, but works fine in the musical typing or keyboard input (strange) Will get back to you over the weekend after I can test a bit, but nothing comes to mind quickly on why this would be happening - I confirm I do see the same result. For now a possible workaround is to use the logic musical keyboard with Midi in enabled in the score editor.