I have a theory that the freezing iMacs have latent hardware issues. It seems that the latest build week for a freezing iMac is week 39 - w/e 30 September. Conspiracy theorists would suggest that Apple became aware of the issue around that time and hardware checks were in place before shipping from that week. To test this, we need to get the first part of the serial numbers from owners of freezing iMacs. Just the first five digits should suffice (any more and they could reveal personal information). The serial number looks like this: W8739 (where W8 = factory code, 7 = the year and 39 = the week). Even if we find that iMacs built after week 39 are still freezing, it would give us an idea if faulty machines are still being shipped. Thank you for reading.