I have not done any professional graphic design work since 2012, I'm forgetting some things but you did just make me remember how difficult it is to find a good printer. The problem I encountered in the beginning was a bit of a racket in that the printers who came up first on Google had all colluded to make the prices high (just like Coles and Woolworths do). You're supposed to get three quotes, you find companies in Richmond and Brunswick that offer you $1100, $1200 and $1150, and you think you're choosing the cheapest. Meanwhile, there is a printer in Bentleigh that would have quoted $600 and one in Frankston South for $575, but their websites would never appear in anyone's search results as they were not optimised to do so. You've got to ask every professional design contact that you have for their best "secret" printer tip and then maintain a good relationship with that person, which is where you've got to make sure you don't piss them off in the ways that I outlined.
Sounds like I've had the luxury of good Productions managers my whole career and you've navigated the more challenging aspects of self employment? That sounds like a nightmare! Luckily for me the quotes are always taken care of and I can just pick up the phone and speak directly to the printer if I have any questions or problems. You've still been spot on despite the amount of time you've been away from the industry and I hope anyone on this board who needs advice on preparing artwork comes back to this post or contacts you for help.