The use of variables in the From and To field inside an FTP job is not possible anymore.
Once any follow up action is done the values switch to either a connection object name or Agent file system.
Defect.
Release : 4.0.7 and higher
Component : RA FTP
Update to a fix version or a newer version if available.
Article title: How to register to Broadcom Software Product updates and Critical Alerts
https://knowledge.broadcom.com/external/article?articleId=133819