Repository: next.js
Issue: formData with app router: Upload error: TypeError: Failed to parse body as FormData.
Labels: bug

### Link to the code that reproduces this issue

https://codesandbox.io/p/sandbox/twilight-flower-v6pl9s

### To Reproduce

i am uploading a  file using axios in a client side component in this way:
```
        const options: AxiosRequestConfig = {
        headers: { 'Content-Type': 'multipart/form-data' }
      };

      const { data } = await axios.post<{ success: boolean; }>(
        '/api/upload',
        formData,
        options
      );
```

in the **/api/upload** route i have the following code:
```
export async function POST(request: NextRequest) {
  try {
    console.log('in post');
    let formData = await request.formData();
    console.log('formData', formData);
    const file = formData.get('file') as File;
  } catch (error) {
    console.error('Upload error:', error);
    return NextResponse.json(
      { error: 'Failed to upload file' },
      { status: 500 }
    );
  }
}
```

if the file is <~2GB everythings is working, the formData is returned with the correct values, otherwise if the file is bigger i get the following output:
```
Upload error: TypeError: Failed to parse body as FormData.
    at node:internal/deps/undici/undici:5668:27
    at successSteps (node:internal/deps/undici/undici:5712:27)
    at fullyReadBody (node:internal/deps/undici/undici:4609:9)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
    at async consumeBody (node:internal/deps/undici/undici:5721:7)
    at async POST (/Users/539hex/dev/deft.cx/.next/server/chunks/_bc0f62._.js:282:24)
    at async /Users/539hex/dev/deft.cx/node_modules/next/dist/compiled/next-server/app-route.runtime.dev.js:6:55831
    at async eO.execute (/Users/539hex/dev/deft.cx/node_modules/next/dist/compiled/next-server/app-route.runtime.dev.js:6:46527)
    at async eO.handle (/Users/539hex/dev/deft.cx/node_modules/next/dist/compiled/next-server/app-route.runtime.dev.js:6:57165)
    at async doRender (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/base-server.js:1353:42)
    at async cacheEntry.responseCache.get.routeKind (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/base-server.js:1575:28)
    at async DevServer.renderToResponseWithComponentsImpl (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/base-server.js:1483:28)
    at async DevServer.renderPageComponent (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/base-server.js:1911:24)
    at async DevServer.renderToResponseImpl (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/base-server.js:1949:32)
    at async DevServer.pipeImpl (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/base-server.js:921:25)
    at async NextNodeServer.handleCatchallRenderRequest (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/next-server.js:272:17)
    at async DevServer.handleRequestImpl (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/base-server.js:817:17)
    at async /Users/539hex/dev/deft.cx/node_modules/next/dist/server/dev/next-dev-server.js:339:20
    at async Span.traceAsyncFn (/Users/539hex/dev/deft.cx/node_modules/next/dist/trace/trace.js:154:20)
    at async DevServer.handleRequest (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/dev/next-dev-server.js:336:24)
    at async invokeRender (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/lib/router-server.js:173:21)
    at async handleRequest (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/lib/router-server.js:350:24)
    at async requestHandlerImpl (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/lib/router-server.js:374:13)
    at async Server.requestListener (/Users/539hex/dev/deft.cx/node_modules/next/dist/server/lib/start-server.js:141:13)
 POST /api/upload 500 in 9203ms
```

### Current vs. Expected behavior

I expect always to have the formData returned despite the file size

### Provide environment information

```bash
Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.1.0: Thu Oct 10 21:03:11 PDT 2024; root:xnu-11215.41.3~2/RELEASE_ARM64_T6020
  Available memory (MB): 32768
  Available CPU cores: 12
Binaries:
  Node: 23.3.0
  npm: 10.9.0
  Yarn: 1.22.22
  pnpm: 9.12.1
Relevant Packages:
  next: 14.2.18 // An outdated version detected (latest is 15.0.3), upgrade is highly recommended!
  eslint-config-next: N/A
  react: 18.3.1
  react-dom: 18.3.1
  typescript: 5.6.2
Next.js Config:
  output: N/A
 ⚠ An outdated version detected (latest is 15.0.3), upgrade is highly recommended!
   Please try the latest canary version (`npm install next@canary`) to confirm the issue still exists before creating a new issue.
   Read more - https://nextjs.org/docs/messages/opening-an-issue
```


### Which area(s) are affected? (Select all that apply)

Not sure

### Which stage(s) are affected? (Select all that apply)

next dev (local)

### Additional context

i tried also to update to next 15.0.3 and i have the same exact issue.