Build plate residual image

On my Mini, the area where the octopus model was printed in outgoing test is shiny. An octopus silhouette is thus present on the bottom of all the prints. How do I make the texture of the build plate uniform?

Refinish your PEI print surface with a light bit of sanding: https://www.lulzbot.com/learn/tutorials/pei-print-surface-maintenance