Is it possible that the thick walnut HD engrave settings is wrong? I realize that different wood types need different settings even in plywood to penetrate through the veneer, but thick walnut HD engrave settings default to 250/6
Did you use a LPI of less than the 450 that the Proofgrade setting calls for? I think high LPIs engrave deeper (because of overlapping lines) and that’s why the power setting is low.