Why does my SFTP server application called "freestpd.exe" located in my Main Poller stop out of the blue, for the Orion VNQM module?

I have a Main Poller with the VNQM module working in conjunction with the FTP Server application "freeFTPd".

The VNQM calls stop being processed from one moment to another by the FTP Server and it is not until I restart the application that they are processed again.

Has anyone else encountered this problem?

It is worth mentioning that, this usually happens once a day at approximately 19hrs.

I appreciate any kind of help.