On our free PBX system - it appears that all incoming calls are being displayed as anonymous. the call logs show the caller name and number but in the dial section it reports as Anonymous. And the phone display as Anonymous. Our lines come in as analog and are routed through a patton. the provider has no restrictions on the line and says they are not blocking id.
screen shot from log
I recall this coming up a few weeks ago.
If the CNAME/CID information is correct in the logs, you are getting the information from somewhere. The question then is why is the information got getting propagated out to the phones?
I think the solution in that case was to change something in the SIP header (the “From” header instead of the other header??). If you can, check back through the old postings looking for your problem (I think the word anonymous was in the description) and see if that sounds familiar.