TYPO3 Core

I guess this is due to the usage of

foreach ($tsfe->rootLine as $rootLinePage)

in ContentObjectRenderer. Since the rootline includes the current page as well, we have to make sure to exclude that from the slide.

From
\TYPO3\CMS\Backend\View\BackendLayoutView::getSelectedCombinedIdentifier

                $rootLine = $this->getRootLine($pageId);
                // Remove first and last element (current and root page)
                array_shift($rootLine);
                array_pop($rootLine);
                foreach ($rootLine as $rootLinePage) {

So this is actually done there, but FE rendering is not consistent. typo3/sysext/frontend/Classes/ContentObject/ContentObjectRenderer.php:5951

Patch set 2 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/44365

Patch set 3 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/44365

Patch set 4 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/44365