I had the same problem a little while ago.
You can disable the kiosk mode by pulling the enterprisehomescreen.xml file from the device to a PC.
This file contains information about the settings in EHS, for example kiosk mode and what app to use for it.
you can find the file in the /enterprise/usr/ directory. But pay attention: The folder is invisible at first. You need to type in the adres bar /enterprise/usr/. the copy to the root of /sdcard/ and copy it to pc. When you finished editing it on notepad++ for example, copy it back to the enterprise/usr directory.