Hi ,
Thank you for the additional investigation and information that you provided related to this issue. I believe you were able to pinpoint the cause of the issue, and it looks like it may be something inadvertently broken in 4.7. I was able to reproduce the same error message that you reported in 4.7, but when I tried the same code in 4.6.1 it worked fine. I have entered a report of my observations to have this investigated further (UE-11256).