Global Upload Trasfers endlessley retry and uses all threads

My son said I should switch to SmartFTP "It's much better." I downloaded the trial but since it doesn't work I am reluctant to proceed with the purchase.

THE PROBLEM
I follow the basic tutorial to drop files onto the Queue Source then, the remote server, then click the play button on the Global Queue.

Files will start uploading using multiple threads. Then one file will retry ("waiting to retry") then retransfer. Soon another file will get into this mode, and then another until all threads are busy with these endless retries.

The file size of the uploaded file will continue to grow, each time it retries. It appears as if the files transfer successfully as I can download them ok, I I have no confidance in what has successfully transfered.

ALSO
I have not found any technical documentation other than basic tutorials and this forum.

Is this a problem that is easily fixed if I buy this product.