TYPO3 Core

I've wrote an extension with image upload in TCA and somtimes is the button "Select & upload files" missing.
Example: I open data set first time - button missing. I open data set second time - button is visible.
This button is to do a multi upload of images. I can see the button in HTML.
I believe the issue is in the file DragUploader.js (typo3/sysext/backend/Resources/Public/JavaScript/DragUploader.js).
There is a condition "DnD: 'draggable' in document.createElement('span')," (row 48) and maybe this is sometimes called to early.
This behavior is in Internet Explorer 10 + 11 and Chrome 38.
If I open the console in Internet Explorer (F12) and open the data set, the button is always there.
System:
Windows 7
Typo3 6.2.4 + 6.2.6

TCA:
'bilder' => array(
'exclude' => 0,
'label' => 'LLL:EXT:...attribute.bilder',
'config' =>
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::getFileFieldTCAConfig(
'bilder',
array('maxitems' => 10),
$GLOBALS['TYPO3_CONF_VARS']['GFX']['imagefile_ext']
),
),