That wouldn't be a big surprise - the ancillary components on the BMC are rather less than stellar, though they get the job done well as assembled. It would be easy to have a less than perfectly round stem "hole" that one would not notice on the aluminum bars. I am not moving as quickly as dayday82 to modify/trim weight on my BMC, but I will likely look at a stem replacement when I change the bars.

The other possibility that hasn't been explored is out-of-roundness on the part of the econo-carbon-bars. That would be an issue, too.

And to those who ask "Why would you keep tightening once you heard a cracking sound?" - what does it matter? Once you hear the cracking, failure is happening at some level. The bars are no less useable now than they were when the cracking sounds were first heard.