Verified in Satellite 6.2.7 Snap 1 Successfully attached multiple VDC guest subscriptions to an activation key. See attached screenshot. If this issue presents itself again, ensure to attach the offending manifest to allow for more specific reproduction.
Created attachment 1240816 [details] verification screenshot
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2017:0197