SFTP fails with ERROR: Write Failed

Hi All,
Iam new to SFTP and i was given the task to code and test the sftp for our jobs (our team is moving from FTP to SFTP).
Iam using SFTPg3 for the command line commands. I was able to transfer the same file with GUI but not on command line. To check the right permissions i have transfered a file with 9KB data with command line options. Can you please help me out
1st Issue: Write Failed error.
2nd Issue: SFTPG3 command on command line is for some reason calls both broker exe and GUI exe. IF the GUI exe pops up on Task manager. The SFTPG3 command doesnt work at all. Is their an option to disable GUI (other than re-naming or deleting exe).
sftpg3 --B C:\Test\SFTP.cmd  --exclusive --Password=****  username@FTPserver
in SFTP.cmd
Put C:\Test\Files\TestFile.txt
Thank you in Advance.