I downloaded your file and uploaded it fine with twython, so it's pointing towards a connection issue, but I would expect to see different error messages if your connection was dropping out. So it's a bit confusing.
I've got one in progress now. The last couple worked fine when I kept phone (connection) close to the camera all the way through. It's been upto 10ft away on this one so might fail. If it does it's definitely maybe something to do with the connection.
I downloaded your file and uploaded it fine with twython, so it's pointing towards a connection issue, but I would expect to see different error messages if your connection was dropping out. So it's a bit confusing.