[Overdriven]

You might want to check for binding in the shaft at ride height. I know it might be hard to do but, the slider has to be the perfect length. If it's too long it'll put pressure on the universal joints, too short and the slider will fall apart. Also check the angles, too steep of an angle will pit pressure on it, although from the pics that looks like it should be fine.

Only things I can think of. Those shafts will wear. But typically the hole for the universal pins becomes egg shaped from the power. Getting hot and melting leads me to believe there's binding.