Brother HL-7050N - Manual (Page 181)

6 - 13 TROUBLESHOOTING
HL7050_US_UG_FM5.5
4 Put the paper tray back in the printer.
5 Open the top cover of the printer, and then close it to resume
printing.
Do not pull out the upper paper tray while paper is feeding
from a lower paper tray because this will cause a paper jam.