Dexter Axles

Here is one for you. My friend has had tires blowing on one side of his trailer on about every long trip. Even changed one of the axels. I recently while following him noticed that one of the rear tires was wobbling. Loose wheel, no. bent rim no. Loose or worn bearing, no. So repacked bearings and re installed wheel, still wobbled. Put another wheel on it, still wobbled. Removed the drum assembly from the other axel and installed it on that axel---wobble GONE. Cleaned the drum bearing area real good and discovered that the milled, drilled, whatever wasn't machined correctly. Put on a new drum and problem was gone. Trailer was 6 years old--China drum?