Question Samsung SCX-4300 - Sensor issue?

Aug 5, 2020
When I try to print, every time, even just 1 page from the tray, the printer gives Paper Jam 01 error. I notice that every time, 2 pages get picked up. I then open the front panel door and close it, and the printed page has roll crease at bottom but comes out along with useless 2nd page.

I searched online and tried the trick of feeding card stock all the way through feed from manual feeder, had it come out from front and also back and this works. Printing is ok with manual feed from front. It is only when tray feed that problem occurs. I cleaned the large-ish rubber paper pick up piece with alcohol, no change.

I found out how to enter Engine Test Mode, and even if I am not too sure how to use these tests, I think I did the the sensor tests correctly and all but one sensor test seem to indicate that sensors are OFF. Feed, Exit, Cover and Manual sensors = OFF, and Empty sensor = Paper exist. I am not a tech although I can easily follow instructions (I got this far on my own...), and am at a loss as to what I can do. Thanks in advance for any help you could provide! :)