node-html-to-image on Vercel serverless function

According to this Vercel page it seems like using a Vercel function to run Puppeteer should be doable, but not matter what I do, I end up with Unhandled Rejection: Error: Unable to get browser page. How can I achieve this successfully?

Here's my current setup:

let customPuppeteer = {};
        let customExecutablePath = {};

        const isVercel = !!process.env.VERCEL;
        if (isVercel) {
          const puppeteer = await import("puppeteer-core");
          const chromium = (await import("@sparticuz/chromium")).default;
          const executablePath = await chromium.executablePath();
          customPuppeteer = {
            puppeteer: puppeteer,
          };

          customExecutablePath = {
            args: [
              ...new Set([...chromium.args, "--no-sandbox", "--disable-gpu"]),
            ],
            executablePath,
          };
        }

        const imageBuffer = (await nodeHtmlToImage({
          html: sizedHtml,
          type: "png",
          quality: 100,
          ...customPuppeteer,
          puppeteerArgs: {
            defaultViewport: {
              width: size.width,
              height: size.height,
            },
            timeout: 60000,
            ...customExecutablePath,
          },
        })) as Buffer;

I sometimes get other errors related to failure to launch Chrome altogether, or failure to reboot Chrome. But never once has this run successfully. (It works as expected in dev).