I have encountered a problem browsing into an empty folder (directory) using FTPES on a Linux server with the cPanel hosting software. On an empty folder, the software pauses a long time then gives a spurious error message. Afterward, normal browsing resumes.
This may be a problem on the server side, as have similar difficulties with FileZila (ugh). This behavior is confirmed by the hosting vendor, Cyon AG in Basel, who might have more information about cPanel versions.