A friend of ours had a Blue OX tow bar failure last month. Brand new tow bar fail after 8 hours of traveling. It totaled the car. Apparently it one of the arms broke at the threads. The break was inspected by an engineer and he noted that the threads were "cut" in to the based material and this caused stresses that broke the metal at the threads. Apparently "rolled" threads would have been better in this application as there would be less stress in the metal.
What is disappointing is Blue OX attitude. When he call their attitude was S!!! happens, you want to buy another one of our bars to replace the one that broke. He politely told them no thanks. Nice to see they didn't stand behind their product.