Spread Axel Flatbed Problem

Several things could come into play here. Recent brake job? Different quality linings? Its possible that the linings anchor & cam ends are backwards on the shoe but a good mechanic should spot that. Balanced weight distribution? Are the other 3 working "too well"? I carried a digital infrared thermometer (pistol type) withe me and every couple week after a few normal loaded stops, I would go around & check the temp. of each drum on all axles and document the findings on a notepad. This will tell you how well your brakes are balanced. This might help the mechanic find your problem.

 

Check airbag? Deflated? That will cause what you describe.