For all A6M5b Zero and later types, when you pick IJN or IJA as the airforce, having markings ON draws some extra clutter on the left side of fuselage. Right side is normal, they don't appear there. I have highlighted the "smudges":
They seem to be some number graphics that have gotten "lost", as they're the same colour as the fuselage number. I'm currently using vanilla 4.12.2m without any jsgme shenanigans, but I'm not 100% sure if it's my install. But is not fatal bug.
Also, the Luftwaffe Do-335 rudder number (when markings are on, of course) on the left side is drawn a bit too close to the leading edge, so it's drawn only partially.