Darkroom, the default scheme, paired Manrope for body text with Syne for headings. Syne is a display face whose heavy weights grow steadily wider, and at hero size, in weight 800, the home page title turned into a row of stretched letterforms. The owner sent a screenshot and one sentence.
The fix was one font. Space Grotesk keeps the same geometric, slightly technical feel at a normal width and reads cleanly at every size the site uses. The other three schemes kept their faces: IBM Plex Mono for Blueprint, Fraunces for Field Notes, Archivo for Studio.
A lesson for the next scheme: check the heading face at the largest size on the site, not just in the type specimen.