An agricultural machine intended for wrapping of round bales with stretch film showing at least one pre stretcher (3, 4) for the film, further at least two mainly horizontal support rollers of witch at least one of them (12) is driven to rotate the bale (10) around its horizontal centre axis (11), a device (5, 6 and 8) to make it possible that the film from the pre stretcher is applied around the bale (10) and where a sensor (9) register the load of the drive unit (8) and an electronic control unit on the base of this information determinates if film disturbances is on one ore on several of the pre stretchers.
