Couldn’t find FXAA pass in postprocessing (three.js/examples/jsm/postprocessing at dev · mrdoob/three.js · GitHub). Did you mean FXAA shader? I tried SMAA and TAA postprocessing passes, but it didn’t fix it.
On the other hand, I tested this on Firefox and it looks perfect over there. So it might be some browser issue. The screenshots above were taken in Safari.
Any way to make it look right on Safari?