TYPO3 Core

In case you need the correct behaviour until the fix is not merged, here is how you should work:

    protected static $previousFolder;

    /**
     * @param Folder $folder
     * @param string $newName
     */
    public function preFolderRename(Folder $folder, string $newName): void
    {
        static::$previousFolder = $folder;
    }

    /**
     * @param Folder $folder
     * @param string $newName
     */
    public function postFolderRename(Folder $folder, string $newName): void
    {
        if ($folder->getIdentifier() === static::$previousFolder->getIdentifier()) {
            // This is a known bug: https://forge.typo3.org/issues/92790
            $newIdentifier = dirname($folder->getIdentifier()) . '/' . $newName . '/';
            $folder = $folder->getStorage()->getFolder($newIdentifier);
        }

        // your code here
    }

Of course, if you know the bug is there (by testing the TYPO3 version), you can just compute the correct new $folder without relying on the dynamic check.

Patch set 2 for branch 9.5 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/66566

Patch set 3 for branch 9.5 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/66566