Write line by line in a file present at SFTP from webMethods 10.1

Hi,

I have to write multiple times to a file located at SFTP. I am using sftp:put to write contentstream to file. It writes 1st time, but from next time, it does not write anything in the file and errors out with error code4.

Steps I am following are :
login to sftp,
use ls and cd to go the directory where file is located,
write data to file using sftp:put and then
do not logout

2nd time when I write, I use same sessionKey

Do you see any meaningful description of the error message?

Alternatively, check with the SFTP server admin to check logs on their end while you run the service from wM. Also, share the current IS fix levels.