Hmm, I think we lost the way here. Shadow copies are not taken off the external drive. One of your partitions are storing its shadow copies on this drive. Look the error message again:
"The shadow copies of volume \\?...06-11de-a7d0-0024e851c5d5} were aborted because volume \\?...06-11de-a7d0-0024e851c5d5}, which contains shadow copy storage for this shadow copy, was force dismounted."
!!!because volume \\?...06-11de-a7d0-0024e851c5d5}, which contains shadow copy storage for this shadow copy, was force dismounted!!!