I can see in the log that WinSCP has asked the server to rename /apps/pms_v1/backend/storage/app to /apps/pms_v1/backend/storage/app1. That seem all right to me. I do not think the problem is on WinSCP side (or can you rename the file using any other SFTP client?). By mv command, I assume you mean shell command, not WinSCP scripting command, right? As a fallback solution, you might try using SCP protocol with WinSCP for the rename. Or setup a custom command to run the shell mv.

I've been using WinSCP for many years. For a few days now, I haven't been able to rename folders using the GUI. Files still work. If I rename the folder directly via the command line using the mv command, it works. The strange thing is that I can then rename this folder using the GUI as well. The log file is attached. Renaming starts at line 400.