I’m confused by how this happened, as I was testing the betas and thought it was fixed. Weird. In the 2021 R1.1 release version (and prior betas) it looks like the file is getting truncated at 1MB approximately.
In any case, if you are using WebFileUploader and need this to work today, you can go back to 2021 R1 and use the hack here: WebUploadedFile Trouble - trailing line added - XML trouble - #4 by Mike_D