Not sure which part of the forum this belongs in, but I'll put it here for now. We make PCBs. Some with hundreds of components each. 1 PCB in several thousand might (for example) have a solder bridge short-circuiting two components together. It never happens in the same place, and can happen on any type of PCB (we make several hundred different types for some 20 - 30 different customers). The customer finds a defective one and asks me to complete an 8D report on the RC and CA. What can I possibly put down for this? It's a total fluke. Out of a million component joints, there will always be one with a solder bridge that isn't picked up by inspection... What would you put?!