Weird behaviour of readMultipartFormData on Azure

[ThibaultVlacich]

I'm using readMultipartFormData like this in a nitro endpoint :

const rawBody = await readMultipartFormData(event)
const rawFile = rawBody.find(partData => partData.name === 'receipt')

But the rawFile I'm getting seems to be corrupted or something that I can't really explain.
The file I'm uploading is 15Mb. When I'm testing on my local machine in dev mode, rawFile?.data.byteLength is correct and equals 14966
But when deployed to Azure (SWA + managed function) it's 21794

I genuinely have no idea what could explain this difference. The actual request in the browser is fine, and Content-Length is the same as when I test in local.
Anyone has experience with uploading files to a nitro backend on Azure, who noticed the same behaviour / how to fix it ?