There are small scratches and holes as shown in the picture. The optical window and resin tanks are clean and modeling is clean. However, this does not always occur in all modeling, but it is steadily continuing. Why is this?
The reason why the modeling is pink is that I painted it to make it look better
That really looks like dust causing small holes in your prints. You say your optical window and resin tanks are clean, but I think you should look closer, use a really bright torch shining sideways to check the top AND bottom surface of your optical window, and the bottom surface of your resin tank.
Also check inside the resin tank silicone, there can be dust particles cast inside the silicone - especially if you’ve replaced the silicone yourself, although I’ve found occasional embedded particles in resin tanks fresh from Formlabs.
If you post a picture of your form file with the print orientation it will be easy to confirm it’s a dust problem, since those holes are showing a definite alignment. If they line up with your print orientation, then it’s definitely dust.
If your optical window and resin tank really are completely free of even the smallest dust particles - but the form file orientation lines up with the hole orientation, then you’ll want to talk to Formlabs support about dust on the mirrors.
As @KevinHolmes mentioned, that does look dust obscuring parts of the optical path.
If you’re not seeing any dust, one way to test this is to print the same part on a different section of the tank. If you’re noticing the same artifacts, this is likely to be due to print setup in PreForm and if not, there’s likely dust obscuring the optical path.