The railway companies had no control over the maintenance or design of private owner wagons (many were very poorly maintained and crude in construction - and many of the 'private owners' actually leased their wagons from the wagon builder, adding a further layer of complexity to maintaining the vehicles) but were legally obliged to operate them. This led to frequent delays and breakdowns due to broken couplings, faulty brakes and hot boxes - the latter caused by the crude grease-lubricated wheel bearings often used on private owner wagons - and problems caused by the simple dumb buffers that were near-universally used up to the time of World War I.