I have run into the same error. And I think I have have fixed it. Open the file s3try.rb and locate:
rescue EOFError => e
# i THINK this is happening like a connection reset
forceRetry = true
$stderr.puts "EOF error: #{e}"
Add these 3 lines:
$stderr.puts "Creating new connection" if $S3syncOptions['--debug']
$S3syncLastBucket = bucket
$S3syncHttp = $S3syncConnection.make_http(bucket)
And save.
Try it out and report the results. It worked for me.