I am getting "terminated by user" / "time out waiting for server to respond" errors

I am getting "terminated by user" / "time out waiting for server to respond" / "software caused connection abort" errors, when I try to upload files from my local to clients SFTP server. First I create a file locally, then move to client's SFTP server. Most of the files get uploaded but few of them error out with this error. Attached is the session log file.

You seem to be getting the errors when connecting, not while transferring. The server might be overloaded temporarily or there can be a temporary network issue. You might just need to retry the connection.

Thanks for the reply... what do you mean when you say "you just need to try the connection".. it is auto task that runs daily and transfer files from source to destination.

I understand. So if the task fails, just retry it:
https://winscp.net/eng/docs/script_retry