what I also noticed, is that the following code returns nothing on Vercel, but works on localhost
new URL(
${locale}/app${path === "/" ? "" : path.replace(/\/(sk|en)/g, "")},
req.url.replace(regexPattern, ${process.env.NEXT_PUBLIC_ROOT_DOMAIN})
)

the formatting is off because of the discord formatting

could it be because of the vercel.json file?