I've had the same issue when getting my van serviced. I used to have a place run by one very skilled dude. Eventually the shop grew and they got some questionable folk working there. I gave him serious feedback when the new guy forgot to tighten the shock absorber bolts that then fell off in Estonia.
He apologised for it and I let it slide as the shop was good otherwise so far. Then they replaced diesel filter and forgot to tighten the common rail high pressure pipe after bleeding the air. The high pressure side runs at around 1500 bar. Guess what happens when there's a loose connector?
A diesel fountain you say? Yes and pretty spectacular one.