Fan, flex and straighten the media before loading it to the tray.
Clean the pick tires with isopropyl alcohol. The tires may be slipping against the media.
Note: Issues with the pick tires slipping may also be caused by the printer's storage conditions - particularly when stored without use for prolonged periods of time, or when stored in hotter environments.
If the issue persists, search for more information related to this issue or contact support for further assistance.