Hi,
The only fix we found was to add a Javascript activity after the SFTP activity, with the below code:
var f = new File(vars.filename); // vars.filename will be automatically set by the previous SFTP activity
logInfo('Old path:', f.fullName); // log full path
var newPath = f.path + f.name.replace(/_\d{14}[a-z]+(\.\w+)$/, '$1'); // generate new path by replacing "{an underscore}{14 digits}{a few lowercase letters}" by nothing
logInfo('New path:', newPath);
f.renameTo(newPath); // move file to the new path
vars.filename = newPath; // set ACC standard filename convention to the new name
This is not elegant but it works well. You may encapsulate it into a function in a Javascript code and call it from within your workflow.
The "File" doc can be found at https://final-docs.campaign.adobe.com/doc/AC/en/jsapi/c-File.html