Carbonless sheets with a thickness of 0 or 1 are delivered to the shift tray, but they are not stacked in an aligned manner in the following cases:
Sheet end curling
If curled sheets continued to be delivered and stacked, these curled sheets may cause both ends of the stack of delivered sheets to be swollen. If this occurs, the paper delivery fan touches the swollen portion, causing succeeding sheets to collide with the sheets already in the stack and be added to the stack obliquely.
Sheet buckling
The tip of an easily-bent sheet may hang down as it is delivered. Depending on the angle at which the tip is hanging, the sheet may be caught on the shift tray, preventing it from being fed. As the opposite end of the sheet is pushed forward, the tip may be curled.
Tip curling-up
A thin, easily-bent sheet may be delivered with its tip bent upwards and curled due to air resistance.