[2.0 next, regressed after rc.13] Loading on latest remains in fallback after a shared source settles #3892

Describe the bug

A Loading boundary using latest(id) keeps its fallback after the source shared by both boundaries has resolved.

Your Example Website or App

Standalone reproduction

Steps to Reproduce the Bug or Issue

1. Use the source below with the selected Solid build (complete setup is linked above).

import { createMemo, createSignal, latest, Loading } from "solid-js";
export default function App() {
  let finish!: (value: number) => void;
  const replacement = new Promise<number>((resolve) => {
    finish = resolve;
  });
  const [id, setId] = createSignal(0);
  const data = createMemo(() => (id() ? replacement : Promise.resolve(1)));
  function load() {
    setId(1); // Replace the source shared by both boundaries.
    setTimeout(() => finish(2), 20); // Every async source is now settled.
  }
  return (
    <>
      <button id="trigger" onClick={load}>
        Load 2
      </button>
      <div id="answer">
        <Loading on={latest(id)} fallback="A">
          <span>{data()}</span>
        </Loading>
        <Loading fallback="B">
          <b>{data()}</b>
        </Loading>
      </div>
    </>
  ); // Wait for 11, then click: it stays A2 rather than becoming 22.
}

2. Paste into a Solid 2 playground. Wait for 11, then click Load 2 and wait.

Expected behavior

Expected: Both boundaries display the final value: 22.
Actual: The first boundary keeps its fallback: A2.

Platform

• Solid: solid-js / @solidjs/web next at 3086f1b77cd7b0431d3a7f768c2984c335758633; comparison 2.0.0-rc.13. Signals, compiler and diagnostics match the selected Solid build.
• OS: macOS 26.6.2 (25G83); browser cases: system Google Chrome 155.0.8059.40. Server-only/type checks run in Bun 1.4.2.
• Builds/comparison: development and production fail. rc.13 passes in both builds.

Additional context

Both Loading boundaries read the same settled source, so both should leave their fallback without another user update.

Related: #2706, #2829, #3524

bun init -y
bun add solid-js@2.0.0-rc.13 @solidjs/web@2.0.0-rc.13 @solidjs/signals@2.0.0-rc.13 @solidjs/compiler@2.0.0-rc.13 @solidjs/diagnostics@2.0.0-rc.13
bun add -d playwright
bun run link-head.ts /absolute/path/to/built/solid
BUILD_MODE=development bun test ./snippet.test.ts