Engraving strips with fabkit

hi i tried to engrave anodized aluminum but noticed that i get engraving stripes how can i prevent this?

Maybe you can use adhesive tape and remove this after engraving.

I can’t understand what you mean by that. These marks come even if I engrave on hot at about the same place

it’s kind of like if
the laser strength would change during lasering
without it being desired can that be?
since I have to laser away a black layer on the shield
and in these areas it just doesn’t quite make it
to laser away this layer
what can I do ?