galderson wrote:

transfer ascii

It's probably because you use ascii/text mode in script, while binary mode in GUI.
https://winscp.net/eng/docs/transfer_mode

I upload the same file using ftp and then using sftp.

Sftp is dropping one character per line of text. (There are 3139 lines of text)

When using the GUI interface and transferring the same file using sftp, it works and preserves all of the characters.

Is there another parameter that I can use in script mode?

C:\ir\data\aa>winscp.com /script=\ir\macros\ftpputmt.cmd /log=winscplg.txt
Connecting to ftp.inforouteinc.com ...
Connected
Starting the session...
Session started.
Active session: [1] tempuser@ftp.inforouteinc.com
transfer ascii
testcase | 308 KB | 670.1 KB/s | ascii | 100%
Session 'tempuser@ftp.inforouteinc.com' closed.
No session.


C:\ir\data\aa>winscp.com /script=\ir\macros\ftpputmt.cmd /log=winscplg.txt
Searching for host...
Connecting to host...
Authenticating...
Using username "tempuser".
Authenticating with pre-entered password.
Authenticated.
Starting the session...
Session started.
Active session: [1] tempuser@ftps.gdom.net
transfer ascii
testcase | 305 KB | 701.1 KB/s | ascii | 100%
Session 'tempuser@ftps.gdom.net' closed.
No session.