I had to do an "ebuild ... digest" for these packages, maybe you should fix the ebuilds... thanks!
Can you reproduce if you delete the tarballs in /usr/portage/distfiles and sync again?
This works, thanks! But I still wonder why this error occurs quite frequently...? Can anyone explain this?
Yes, the tarballs with the same names upstream changed sizes between release candidates and the final release. So if you still have tarballs around from release candidates, you may encounter this.
On that note..