I've set up an IIS 10 FTP server requiring explicit TLS/SSL (an FTPS server). It is only seen by users on the network, with access controlled by Active Directory. I am using FileZilla 3.60.2 to connect to the server, with the intent of rolling FileZilla out to about 100 users on an Active Directory network.
FileZilla connects without issues, but only allows me to browse folders below the FTP root for a minute or so before starting to give me a "550 The system cannot find the path specified" and "Error: Failed to retrieve directory listing." There is one directory that appears in full every time but doesn't appear to be any different than any other directory. The folders being browsed have been set up as virtual directories to available network shares via UNC paths. The server stays connected throughout.
I have double-checked the permissions, which are consistent from the FTP site all the way down -- "modify" permissions are granted.
Oddly, I have no problem with this using WinSCP. Due to corporate policy, I cannot easily change the planned rollout from FileZilla to WinSCP, nor can I determine what's different between the setup of the two of them.
What's puzzling me most is that it works briefly, then stops working. Any clues about how I can troubleshoot this?