Repository: puppeteer
Issue: [Bug]: Setting long viewport and then taking screenshot sometimes generates incorrectly rendered screenshots
Labels: bug,screenshot,confirmed,P3

### Minimal, reproducible example

```TypeScript
const puppeteer = require('puppeteer');

(async () => {
    const browser = await puppeteer.launch({
        timeout: 120000,
        headless: "new",
        args: [
            '--no-sandbox'
        ]
    });

    const page = await browser.newPage();

    await page.setJavaScriptEnabled(true);
    
    await page.goto("file://C:/htmlpkg/index.html", { waitUntil: 'networkidle0', timeout: 240000 });

    const rootElem = '.dl-topic-body__scroll';
    const body = await (page.$(rootElem));
    const bodyBoundingBox = await body.boundingBox();
    bodyBoundingBox.x = Math.floor(bodyBoundingBox.x);
    bodyBoundingBox.y = Math.floor(bodyBoundingBox.y);
    bodyBoundingBox.width = Math.floor(bodyBoundingBox.width);
    bodyBoundingBox.height = Math.floor(bodyBoundingBox.height);

    const width = 800;
    const innerWidthPromise = page.waitForFunction('window.innerWidth == ' + width);
    const innerHeightPromise = page.waitForFunction('window.innerHeight == ' + bodyBoundingBox.height);
    await Promise.all([page.setViewport({ width: width, height: bodyBoundingBox.height }), innerWidthPromise, innerHeightPromise]);

    await page.screenshot({
        clip: {
            x: 0,
            y: bodyBoundingBox.y,
            width: page.viewport().width,
            height: bodyBoundingBox.height
        },
        path: "screenshot-with-setviewport.png"
    });

    await page.close();
    await browser.close();
})();
```


### Error string

no error

### Bug behavior

- [X] Flaky
- [ ] PDF

### Background

I have a js script that takes screenshots of an input html file. Roughly every 50 to 70 executions, the script produces a slightly different screenshot, even if the input file is still the same (and both the script and the input file are unchanged). For example, if you look at [screenshot b](https://github.com/puppeteer/puppeteer/assets/171331383/538341e0-455a-4695-86a5-0b11465baa89), you can see that text “flammable-Modul” is placed further up than in [screenshot a](https://github.com/puppeteer/puppeteer/assets/171331383/e28c9d51-ea79-415a-89a3-0557788738ce). Image [diff](https://github.com/puppeteer/puppeteer/assets/171331383/bd100567-a64b-4c50-8dbe-018abc8fd1df) (created with ImageMagick’s “compare” command) visualizes the difference between screenshot a and screenshot b. Please note I clipped these screenshots to highlight the problem – normally, the screenshots would have a length of over 30k pixels, since they are screenshots of a very long html file.

I’ve noticed that this problem only occurs when I use function page.setViewport() to set a long viewport and take a screenshot of the whole html file. If I don’t use page.setViewport(), the screenshots are always identical. However, I need to use page.setViewport() and set a long viewport, since my goal is to take a screenshot of my whole html file, not only of its visible part.

I am also attaching a zip file with my test data, i.e. the above-mentioned html file and its resources: [htmlpkg.zip](https://github.com/user-attachments/files/15511398/htmlpkg.zip)

### Expectation

If I run my js script several times, the resulting screenshots are always identical.

### Reality

If I run my js script several times, the resulting screenshots are not always identical: sometimes, some text elements have a slightly different position.

### Puppeteer configuration file (if used)

_No response_

### Puppeteer version

22.10.0

### Node version

18.19.0

### Package manager

npm

### Package manager version

10.2.3

### Operating system

Windows