Mismanaged defects can cost a company £ millions later. Typically, when repairing a major road, the first task is to scrape off the top layer of the old road. Only after this has been done can the state of the road underneath be determined.
If the road is in good shape, then the top layer can simply be replaced and all is well. But if it transpires that there is profound damage, for example a deep pot-hole filled with loose stones, then the repair needs to be more substantial. Typically it would be necessary to remove more material and rebuild that part of the road from scratch before replacing the top layer. But this is a much more expensive process, and the contractor will need to get approval from the customer (usually the Local Authority or the Department of Transport) before proceeding.