A friend had an intermittent leak behind one of their kitchen cabinets for years... thought it was a cabinet mounting screw that pierced a drain pipe. They finally had the cabinet pulled to find a drywall patch and the pipe segment in the photo below behind it. They were the original homeowners and never had any repairs so this was done by the builder. Apparently someone on the builder's crew or a sub broke this (I assume/hope after the plumbing inspection!) and just slopped it back together with some sort of construction adhesive. Unbelievable.