We experienced something very similar in our environment. In our case, the issue was related to the SYSTEM account not being able to properly create or access the temporary WinSCP log files under C:\Windows\TEMP.

Running the service under a dedicated admin/service account resolved it immediately, just like in your situation. We also noticed that endpoint protection and tightened local security policies on some workstations seemed to make the issue appear only on specific machines.

A few things that may help others troubleshooting this:

• Verify SYSTEM account permissions on the TEMP directory
  
• Check if antivirus or EDR is blocking WinSCP child processes
  
• Make sure the WinSCP executable path is accessible by the service account
  
• Confirm the same WinSCP version is installed across all affected systems
  

It definitely seems like one of those older WinSCP/.NET integration issues that can still resurface depending on workstation hardening policies.

What do you mean by "under the hood"? Can you please be more specific?

By Host I mean the machine where WinSCP runs.

Originally I am getting: WinSCP.SessionRemoteException
but under the hood SessionLocalException is raised.

Just to clarify: By "host" – do you mean the server you are connecting to? Or the machine that hosts the service (the machine where WinSCP runs)?

Also now I have noticed the discrepancy between the subject and the original post text. So are you getting SessionLocalException or SessionRemoteException?

In all the cases we had on some computers it was like that:

1. Host restarted
   
2. Service with WinSCP is working and then at some point later on (usually after a month), it stops connecting to FTP server: WinSCP.SessionRemoteException. Service restart doesn't work. Restarting host solves the issue.
   

Does restarting the workstation help? What does "after some time of usage" mean exactly?

Hi,
On some workstations we got that error. The .net process was run on system account.
After investigation we got more detailed error:

Exception: WinSCP.SessionLocalException: WinSCP process terminated with exit code 3. There was no output. Response log file C:\Windows\TEMP\wscp1C14.00E7D730.tmp was not created. This could indicate lack of write permissions to the log folder or problems starting WinSCP itself.

Restarting service didn't help. Changing user account from system to a user with admin rights did solve the error.

From what I have read, it is been a well known error however it has already been solved a long time ago.