Performing a retorque on the delivery valve holders is easy for a Bosch pump man. I would recommend that you have a Bosch service mechanic do the job on-engine. They have the serrated socket, the copper washers and o-rings if needed, the torque specs, and last but not least, the experience.
Also, ask the Boschman to try loosening one high pressure line at a time in order to isolate the nailing cylinder. Have him do this prior to the re-torque.