CM had an entire batch of CM Quick Fire Stealth units with problems with the soldering and yes, most of the blame goes to Costar, but CM needs to take responsibility as well. It was a batch of around 150 CM Quick Fire Stealths with MX Brown on which the entire area around the backspace key had bad soldering.
They pulled many of them out of the market before it became something even bigger, but it seems a few units are still out there, but yes, they already assumed the error and already took several actions to fix it.
Another problem that occurred during the same time-frame was that a batch of 200 units of ABNT2 (Brazilian Portuguese) layout CM Quick Fire Stealth keyboards had a wrong enter keycap (CM Brazil had to send the correct keycap to everyone who bought it):

In any case, the only way to fix this problem is to contact Cooler Master's support, they should already be aware of the problem.
And anyways, the quality of Cooler Master products varies a lot since they're using multiple OEMs.
Costar (Rapid, Stealth, XT, Trigger) is nice and they know how to get the job done when they want to, but when they **** something up, you get an entire batch of faulty units, plus they're slow and expensive. Also, they're only a middle man, they're only as good as the factory they end up choosing. Not like everyone will use the same factory as FILCO or the one used for Ducky Shine II and III.
Solid Year (Rapid-I, Mech, TK) on the other hand is quite fast and cheaper, their soldering is really nice but their keycaps just aren't good at all and they're partly to blame for the
Logitech G710+ fiasco too.
iOne (CM Quick Fire Pro, CM Storm Trigger Z) "supposedly" has the "lowest return rate" (though I'm not really sure about that), but their reputation is terrible and the fact that
Solid Year has overrun them isn't something that surprises me.
But in the end, it's not always about the OEM, the company needs to keep an eye over them and control what they're doing and yes, that's part of what Quality Control is and something many companies are lacking nowadays.