so.. the situation is, alot of these ledchips are actually defective, but they package them anyway because no one checks.
this happens in alot of the cheaper led products. if you look at those led floodlights under the microscope not all the leds even light up, but because it's a flood light, you can't tell.
it could also be bad drivers, or errant surges on your house circuit, low cost drivers are more sensitive to that.