Given the number of reports (and the fact that this is common enough that I found a youtube video explaining how to swap the DRM chip), that seems possible, but less likely. These chips are not complicated or hard to make. The prior on failure rates should be extremely low. But the next time I need a toner cartridge, I will make sure to test it before I swap the chip, just to double check.
If the chip isn't defective, why did it work with a known good one? If it isn't complicated to make them, why does your chip not work?
To answer these questions, we need to know: what do the chips do? Where did the replica cartridge companies get them from? Etc. You said you would test the chip before swapping, how do you do that? Is it just a flash chip? If it is, why are the replica manufacturers not putting the correct information on it?