First drive after brake upgrade, then - BANG!

Look we are not there and we cannot see. Use your head. One thing is to compare sides. Look at the two adjusters, are they adjusted different or sit different? If a weld has broke at the anchor I would think you could see that even in the "grease." where it's moved. If you can get it up on a hoist with weight off the suspension, pry around and see if something moves that shouldn't.

A failure like this is fairly dramatic, and it really should not be really difficult to pin it down.