For a leak, I'd do one at a time. Sure, you can shotgun it and do both, but I'd only do that if I thought it was a wear and/or corrosion issue that would impact both sides.
Why did it break (or leak)? Why does anything break, or wear out? Manufacturing defect, wear, luck of the draw, phase of the moon...
Why did it break (or leak)? Why does anything break, or wear out? Manufacturing defect, wear, luck of the draw, phase of the moon...