I know this problem! I bought sometime 50pcs. only 4 worked!! Money: bye bye!!!
I had a trustable source, but my contact person was fired from his boss....now i have another source, but very expensibe (about 56$ / pc).
A good tipp: Buy only Chips in the black original packing. then you can be 80% sure that they are ok! All bad chips are packed between 2 transparent plastic foils.