Just found something out. If you start the camera and activate flash (to automatic mode), then press the power button (short) and let the phone go to sleep mode: The flashlight works again from the lock screen (also via long pressing the home button) and the symbol in the short cut menu is the right one. If you close the camera app or put it to the background, the error returns and flashlight won't work.
So it might have something to do with the camera app.
Thanks for your feedback! I'll add it to the report for the tech team