Some file downloads are named downloadfile.bin instead of the correct name
This is caused when the download link contains variables that inform a script on the server which file to download. Android's download manager isn't smart enough to figure out what the file name is, so it calles it `downloadfile.bin`.
Downloading from this example link produces an example of this behavior:
Resolving this behavior might be difficult without totally replacing Android's download manager with custom download code and requesting full storage write permissions.