Thanks for your comment. I did receive a kind email from William prior to the return of my points. He stated that SPG has recently experienced several incomplete transfers to Korean Air, apparently, in reaction to a number of fraudulent transfers. Consequently, Korean Air has begun to institute a higher degree of security checks on their end. While I have received no follow-up from the SPG Program Services, I wonder whether it may be related to my middle name (which is included in my SPG profile but not in my Koreanair profile). This has not been an issue with SPG->KE transfers in the past, but since they have instituted a higher degree of security checks this may have led to the transfer being rejected. I have removed my middle name from my SPG profile so both profiles are now identical, and I will try to re-transfer to KE.