Perhaps it's more likely that the Bus was built to a price ( read 'a subsidised low one' ) and / or that to make it meet the predicted ( read 'sales pitch' ) performance it was built a bit ( how shall I say ) 'on the light side' ( in all senses of the phrase ).
I have for a long time harboured the thought that Bus' will not be as 'robust' ( again, in all senses of the word ) as Boeings & MD's as they move into old age.