Each app deals with tag case and punctuation differences in different manners.
In MC, open the Tag Action Window.
Select any two affected tracks.
Look at the Artist and Album Artist tags. For each tag, if the tag is exactly the same for the two tracks, MC will show this single value. If they are different, MC will show <varies>. This will show the difference.
You can select all the AC/DC tracks, and enter a single value to make your tags all consistent. Then Library Tools > Update tags (from library).
Now you can entirely clear/rescan your SBS library and should see consistent values.