Duplicate of https://forge.typo3.org/issues/107160
Dokumentation says for:
folders.recursive
Type: string / stdWrap
https://docs.typo3.org/m/typo3/reference-typoscript/main/en-us/DataProcessing/FilesProcessor.html#confval-filesprocessor-folders-recursive
But in the code it has no stdWrap feature:
$fileCollector->addFilesFromFolders($folders, !empty($processorConfiguration['folders.']['recursive']));
I would suggest changing the documentation. furthermore it is not string but boolean
code looks like
$fileCollector->addFilesFromFolders($folders, !empty($processorConfiguration['folders.']['recursive']));