Let me answer for Milos http://ntecc.rajce.idnes.cz/milousuv_sutr/

I understand now. Thank you. Of course bends are exaggerated just to see them better. There must be a subtle balance of pushing force. Too little -> noise, too much -> friction. At least now I am sure the noise is exactly like that: the bronze synchronizer ring rattling on steel 5th change gear. When the gearbox gets warm, parts expand -> no more play -> no more noise. Very logic.