Ok,
I'm still working through this issue - but I think I figured out one part.
If the Accept-Encoding is blank, it defaults to gzip. So I simply set the Header with a Accept-Encoding of blank ("") and it no long is using gzip.
But the size of the transfer is still more than the actual file size (by 127 bytes). Seems like it adds extra info, like the filename, and mimetype. So my server expects 127 less bytes...
Bad news is that my server/cloud is throwing a Null Ptr - but I don't know the root cause as I don't have access to that code...
One hour to code and 16 hours+ to figure out why it doesn't work. :-)