Getting artifacts on an imported image after union
I have a phone case file that I want to make some slight modifications to. Initially it was working and I 3d printed the first prototype, made a change, printed another. On the third iteration that I printed I noticed a bunch of pitting in the object that was not there on the previous prints. At first I thought it was a printer or filament issue, then on closer inspection I see a bunch of artifacts in tinkercad that line up with the issues I had in the print. I tried starting all over again on my tinkercad file but the artifacts keep showing up. It seems that after I bring about 3 hole objects in and then do a union the artifacts show up. I started a new project and end up with artifacts there also. Does anyone know how to prevent this? (2 images included)