Originally Posted by
-bart-
cod due to back reflection is indeed uncommon. Although it's more likely to happen when fiddling around with optics. Suddenly, for one split pico second all conditions are right, you create an external cavity, and poof !
Due to fabrication tolerances, if you replace your diode your laser-die will never be in the same place twice, and point in the same direction. So a double backreflection death is extremely unlikely.
Don't rule out esd, it's not always an instant killer, propagated delayed defects will kill eventually too. Short your diodes as soon as you receive them, if not already. And unshort them when connected to a lasorb.
Swap your drivers to rule out one of them causing havoc.