When the first year of GMC's New Look buses showed nothing but problems, GM fixed them and the design went on to be the most successful North American transit bus ever.
When the first Siemens DuWag LRV's were being assembled in Edmonton the Siemens technicians had sheets headed "Nicht für Dritte" (= Confidential proprietary info), so of course I came back while they were at lunch and read. It was case by case every problem in setting up the mother fleet of Frankfurt U-2 Stadtbahn cars, with the solution recorded. This was reassuring to me, as they were new in the North American market.
I agree that investigating the problems should include the maintenance operation in Chicago. When we visited the original San Diego Trolley shop in 1981, knowing some German and having a young colleague who was smart and low key made it easier for the DuWag rep there to show us weak points in the shop, including grit that blew in through open doors.
It is possible that rapid expansion has caused Siemens problems, but a good maintenance operation should be able to identify defects, work with the builder, and not just check off the FRA points and send the train back out.