Those artifacts are the result of the ratio of Sampling Point Size to Padding being too small. See link to FAQ here and then Question #2.
The solution is to simply increase the padding value. Typically you want a ratio of sampling point size to padding of about 10%. So if the sampling point size is 90 then a padding value of 9 works well or sampling of 80 with padding of 8. The issue occurs when this ratio is less than 2% ~ 3% when using material properties that are closer to the max range of properties like outline, etc. when the text is zoomed out / small on screen.
The larger the ratio the more range the Outline / Shadow will have but the larger the padding the more texture space the padding occupies thus forcing a smaller sampling point size. When creating font assets, think of how it will be used. If you plan on using an Outline, Shadow, etc. then a ratio of 10% is great. If you plan on having huge shadow offset then a larger padding / ratio will be necessary. If the text will be plain without styling then a smaller ratio like 5% will work and help to maximize sampling quality.