I’ve had this in several versions: it will often be impossible to put the end marker (or the cursor) after the last event in a song. I haven’t found any pattern for how it starts, but once it happens it seems to stick. Would be great if this could be fixed.
Yepp, I experienced this a few times too but haven’t got recipe how to reproduce.
My workaround was to manually re-type EndMarker location-time first (to a “later time”) to get things done.