Fix timeline rescale glitch

app/scripts/components/exploration/hooks.ts

@@ -66,7 +66,14 @@ export function useScales() {
   const scaled = useMemo(() => {
     if (!main) return undefined;
     return rescaleX(main, zoomTransform.x, zoomTransform.k);
-  }, [main, zoomTransform.x, zoomTransform.k]);
+    // We want to scale this scale only when the zoom transform changes.
+    // The zoom transform is what dictates the current timeline view so it is
+    // important that it drives the scale. Because the main changes before the
+    // zoom transform we can't include it in the deps, otherwise we'd have a
+    // weird midway render in the timeline when this scale had reacted to the
+    // main change but not to the zoom transform change.
+  }, [zoomTransform.x, zoomTransform.k]);
 
-  return { main, scaled };
+  // In the first run the scaled and main scales are the same.
+  return { main, scaled: scaled ?? main };
 }