Small update on this, Axel Reinhold faced an apparently different issue on an SVN server until we noticed the requests were sent in small chunks cut before the CRLF and experiencing the same problem. He could confirm the patch fixes the problem for him as well, so I'm going to merge the patch now.
"cas", if you want to be credited as a reporter of the issue, you need to raise your hand very quickly now, because once the patch is merged it will be too late. Best regards, Willy