TYPO3 Core

\TYPO3\CMS\Core\Resource\ResourceStorage::isWithinFolder()

    public function isWithinFolder(Folder $folder, ResourceInterface $resource) {
        if ($folder->getStorage() !== $this) {
            throw new \InvalidArgumentException('Given folder "' . $folder->getIdentifier() . '" is not part of this storage!', 1422709241);
        }

IMO the $folder->getStorage() !== $this must be changed to $resource->getStorage() !== $this.

After that the exception is gone, but still pasting the folder fails.

Moreover if you copy a folder A located in /B/ and you try to paste it again into /B/ an exception is thrown. It looks like copying folder does not work properly in most cases and only works in some cases when you're lucky.

Patch set 1 for branch TYPO3_6-2 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at http://review.typo3.org/38128

Patch set 2 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at http://review.typo3.org/38125