FTP Put command hangs during transfer - Possible Cisco FMC issue?

We have an internal server behind a cisco FMC that connects via FTP and uses a put command to copy a file to an external server.

As of yesterday, this server stopped sending out the file via FTP. When the script runs to connect to the remote server, it logs in fine, but when the put command is sent it hangs on this:

​

331 Password required

230 User logged in.

ftp> put \\servername\haha\cisco.xml

200 PORT command successful.

150 Opening ASCII mode data connection.

THEN ABSOLUTELY NOTHING

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According to the folks in the office, no one has changed anything (: (: When I google this issue it inevitably runs into a firewall issue for most cases. I looked into our cisco FMC and I can see FTP connections being made between the internal and external servers every time the script is run (every few minutes).

I can connect to the remote server using Filezilla from my desktop, but I do see a security error: Insecure server, it does not support FTP over TLS.

Both the servers are running Microsoft Server 2012. Other research has shown there might be port restrictions in FTP based on some IIS settings there as well, but that is semi unfamiliar territory.

Has anyone here run into a similar issue?