Combino Cracks

Looks like the Combino is having more problems. In 2004, there were issues with car bodies slightly cracking.

On March 12, 2004, Siemens admitted to problems concerning the stability of the car bodies and, as a precautionary measure, instructed all public transportation services to take all Combinos with a service distance of more than 120,000 kilometres (74,565 mi) out of service. Torsion forces generated in S-curves were much higher than anticipated, leading to cracks around the articulations between the car modules. Subsequently, hairline cracks were found in the joints of the aluminium bodies, which could cause the roof to collapse in the case of an accident.

The Caterpillars of Budapest had issues and were delayed due to door issues in 06. While not as bad as the issues the European versions had, Melbourne is going to make fixes due to the fractures that have occurred on their trainsets. I've heard that subsequent redesigns have fixed the problem on the current model.