* Create a new content element, e.g. a textmedia element. * Go to the list module of the page, on which the content element was just created. * Select mulit-selection mode for clipboard (if it has not already been selected). * Go back pack to the page module. * Copy the content element by clicking its top-left icon and selecting "Copy" from the context menu. * Insert the copied element below/above the original element with the now visible "Paste after this record"-Buttons. *Site will reload, no error, but no copy has been created!* Also no record has been added to the tt_content table. The array _$this->clipData['tab_1']['el']_ in the _\TYPO3\CMS\Backend\Clipboard\Clipboard_ class is simply empty. When switching to single-mode, _$this->clipData['normal']['el']_ will hold the correct tt_content reference.