on file com_component\admin\dom\html\form\input\file\default.php at line 97 and around 233:
//Current value is important for the removing features features ()
$htmlHiddenCurrent = JDom::_('html.form.input.hidden', array(
'dataValue' => $this->dataValue,
'dataKey' => $this->getInputName('current'),
'formControl' => $this->formControl,
));
it generates an id like: jform_jform[myfield-current]
to generate a more standard ID like jform_myfield-current
the code should be:
//Current value is important for the removing features features ()
$htmlHiddenCurrent = JDom::_('html.form.input.hidden', array(
'dataValue' => $this->dataValue,
'domId' => $this->getInputId('current'), /* hack */
'domName' => $this->getInputName('current'), /* hack */
'formControl' => $this->formControl,
));