I'm running into the same issue. The only difference for me is a different hex code, but the message is the same. The "Completion status" section of the job log shows:
Final error: 0xa0008488 - Access is denied.
Then under the "errors" section, I see:
Backup - \\MATRIX\Microsoft Information Store\First Storage Group Access denied to database Mailbox Store (MATRIX).
Database or database element is corrupt
I have checked the referenced articles, and when I look at my file selections, in the graphical layout, "Exchange" isn't even an option under "Shadow copy components -> User data". And in the text layout, I see an explicit exclusion for "Shadow copy components\User data\Exchange server\*.* /SUBDIR /EXCLUDE".
I'm stumped.
