Hp 9050 laser jet stacker error

Probably just a bad sensor or dirty sensor causing the issue.

Stacker or stacker/stapler output bins

For the 3,000-sheet stacker or 3,000-sheet stacker/stapler, the output bins are the upper bin (face-up) and the lower bin (face-down).

The upper bin (face-up) is the top bin on the stacker or stacker/stapler. This bin holds up to 100 sheets of paper in face-up order as they exit the printer. A sensor causes the product to stop when the bin is full. Product operation continues when you empty or reduce the amount of paper in the bin.

Lower bin (face-down) is the lower bin on the stacker or stacker/stapler. This bin holds up to 500 sheets of paper and can stack or staple jobs. This bin is the default output bin.