thinking about the reason always the parts printed in the left side of the plate was broken, or miss parts, or fall into the vat, i build another perforated plate, this time, 6 mm thick, and checking against a glass plate, i think is perfectly flat.
scratching my head and checking again the failed prints, voila!, i see a spherical pattern and think inmmediately in the shutter shape.
i suspect, and this night i willk check it, the shutter is not completely open when the projector show the slice. i bet my right ball

im gonna introduce some delay, maybe 500ms in the pre-lift section, just after the M280 command to open the shutter, and another 500 ms delay before close the shutter.