over time, wear and tear on the hinge mechanism and on the ribbon cable will cause looseness in the hinge and slack in the cable, which ends up causing the screen to sit up slightly.
Unfortunately there isn't anything that can be done to rectify this, except return it to Canon for refurbishment, which isn't cost-effective.
Ok, thanks for clarifying!
In that case there is likely an obstruction which will need to be cleared.
If you cannot see anything obvious then it would be best to return the printer to Canon to have the problem investigated.