Status light is red and paper light blinking

Alex,

To isolate the problem, please try the steps below:

Remove and re-insert the paper tray and then click Go.

Take the drum unit out of the machine and put it back in.

Here, I provided you a link that might help you:

http://welcome.solutions.brother.com/BSC/public/us/us/en/faq/faq/000000/000100/000070/faq000170_007.html?reg=us&c=us&lang=en&prod=hl5250dn_all

Have a great day!

The problem is caused by a gear's axis damage. If you pull out the paper tray and remove the lower tray completely, you can see a white gear in the middle of LEFT-HAND side wall. Its axis is broken and causes the gear loose.

To repair it, first power off and remove the power core, remove the toner and drum. Then, turn the printer to side way so that you can see the gear. Put a screw into the small hole used to hold the axis. You may need to first DRILL a hole in order to insert the screw if your screw is not tiny enough.