For grandstaff works requiring extra staves including those with ossia passages the CTRL+SHIFT+UP/DOWN command does not work properly. If the notes have been placed on a stave below the parent staff using this command does not return them to the parent staff but sends them instead to the top staff in the part. If that's an ossia staff or an additional higher keyboard staff, that's where the music goes to. It skips the parent staff altogether along the way. This works the other way too skipping the parent staff on the way down. This is not such a frequent problem I grant you but when it happens it is often impossible to undo and the whole passage requires rewriting.
Idea No. 335