I had the same problem. This forum solved it. Have you tried setting the max memory to 10% in the app’s settings? (per Chamberhouse ) [RESOLVED macOS 26.3] Grid-RGB artifacts with Starlight on macOS 26 (Apple silicon) - #39 by Ted-Leeds
BTW, how is the M4 studio compared to the M1 Ultra speedwise with Topaz?, the figures look very similar.
