There seems to be a problem with GridElements w/Dataprocessor.
If I use the Grid Gallery in a GridElement w/Dataprocessor, there is an error message (1/1) #1476107295 TYPO3\CMS\Core\Error\Exception
PHP Warning: trim() expects parameter 1 to be string, array given in /xxxx/typo3_src-10.4.4/typo3/sysext/core/Classes/Utility/GeneralUtility.php line 1524