To get some light in that dark tunnel - was this a aircraft, which requires a diagonal harness part or not? For example, if this happens in an older C172/F172 it is not a matter of unairworthiness, because the design is based on basic belly harness. Another one - when were the harnesses last changed? They do have a lifetime expired date. The diagonal upper body restraint harness is a known issue with 172s, same as the lever lock mechanism of the doors for newer ones ...