Is it normal procedure to bring cylinder head to machine shop when replacing head gasket?
Unfortunately, the mechanic business is time oriented, so removing a head and sending it out won’t usually happen if the tech is reasonably convinced it is just a head gasket. This will result in the occasional cracked/warped head coming back for further repairs. I really think that something missed by the shop is the shop’s responsibility, therefore the first head job should stand, and they should only charge for the replacement part/s to finish the job. I am also of the opinion that any head job should be sent to the machine shop for magnafluxing/machining as insurance, because loosing that time and labor is just bad business.