My friend made it slightly under a year at Boeing after working for another airline as a maintenance mechanic. The level of quality control at Boeing was so abysmal he quit to work on busses, paying all $20k in relocation back to Boeing.
He takes pride in the quality of his work and adherence to the rules, but Boeing's managers let him know that reporting unwired bolts & incorrectly installed hardware per policy was something they did not do. Very sketchy, not something anyone wants to be signing off on as personally liable!
The management loves to circlejerk about the "Boeing process", but lots of shit is slipping through these days that would have been unacceptable (and firable) only 2 decades ago.