Airdrop security

having issues sending airdropped files from iPhone 12 pro to my late 2012 iMac - i can send them in reverse, and from my MacBook pro to my iMac and from my iPhone to my MacBook pro. I can strangely also send them from my iPhone in certain circs (see attached pic) but i have tried every modality including be visible to contacts only, everyone, none etc

reading here https://support.apple.com/guide/security/airdrop-security-sec2261183f4/web mentions about airdrop hashes maybe not being recognised because when i call up the airdrop map it shows my iMac twice, once in Devices and once in "Other People categories" - please see the attached pic where the iMac WILL receive files by my selecting it in Other people but hangs on waiting if i select devices - ive tried all the usual reset bluetooth etc but to no avail.

Any ideas? everyone

Cheers