TYPO3 Core

Got some time to test this out. Two changes needed:
The inner loop must be (note the true argument at the end):

foreach ($rootLevelFolder->getSubfolders(0, 0, Folder::FILTER_MODE_NO_FILTERS, true) as $subFolder) {

(not sure about the filters, I just disabled them, because inside the loop the folders are selected for recycler folders anyways)

And the break inside the inner loop must be removed, so that it actually loops over all folders.

These both steps let the task cleanup all recycle bins, just like one expects from this task.

Or to put it all together, this is how the loop looks now in the patched RecyclerGarbageCollectionTask in my project:

foreach ($storageRepository->findAll() as $storage) {
    $rootLevelFolder = $storage->getRootLevelFolder(false);
    foreach ($rootLevelFolder->getSubfolders(0, 0, Folder::FILTER_MODE_NO_FILTERS, true) as $subFolder) {
        if ($subFolder->getRole() === $subFolder::ROLE_RECYCLER) {
            $recyclerFolders[] = $subFolder;
        }
    }
}

@S P

Could you please also test your changes with _recycler_ folders nested inside other _recycler_ folders if it crashes ?