Hi Peter
The module determines the child messages' filename from the attachment's content type. Please refer below to the comment for the logic of that part.
// Filename normally is included in the name parameter
// It can be enclosed in double quotes
// It can also be followed by other parameters or white spaces
// Some sample below:-
// text/plain;charset="UTF-8";name="file.txt" ;otherParam=ParamValue
// text/plain; charset=us-ascii; name=sample.txt
From the RWB audit log, it looks like the file name of the trigger file test3.jpg is being set as the attachment's filename. Can you double check your SFTP module coding on the part that sets the attachment names? I see that the variable Filename is used in many places, maybe it is causing some shadowing issue. Try to use unique variables for filename of the trigger file and also filename for the list of files from SFTP server.
Rgds
Eng Swee