Myself, working in an industry that subcontracts jobs to other parites, I see this kind of delay all the time. Your business is only as good as your weakest link (so to speak) perhaps it's time to think about what other parties your business associates with and possibly find more reliable ones.
It's sad that it comes to stuff like this, but when a customer is paying for service and not getting it, they get upset.
There's 934893489 shops out there, all of them have bad stories, and all of them have good stories (which far outweigh the bad)
Pro tip: Take every story with a pinch of salt and make up your own mind.