OK, I made another test. Remove WTB and close front door.
1. Machine will complain about "Waste Toner Box installation failure"
2. Next open front door and install back WTB, machine still be showing on display "Waste Toner Box installation failure" without closed door but...
3. On display you can choose by arrow machine to display next page of animation guide and one can see that "There is open component" message

Tested on 8 and i-series machines. So all guys who think animation guide is not that important...be prepared