As everyone knows, the supply of semiconductors is pretty bad now. Normal suppliers such as Digikiey have zero stock. Recently we have had to purchase from less known distributors, mainly from China. We are getting a rather high defect rate, maybe 5%. We aren't sure if its a PCBA problem or a chip problem. We have been told the chips are "repackaged", whatever that means. There is not indication that these are used, repackaged, recycled, etc.
Are there any known cases of counterfeit chips coming from China? Is there any way to detect this? We use about 5000 chips per month, so this is a pretty serious problem for us.