What can cause a long FTP response?

Question

FTP

Good day, the bottom line is this: there is a website, it works stably, it loads quickly, no problems ... however, when I connect via FileZilla, or via SublimeText (FTP), the response is 5 seconds ... respectively, opening folders, downloading files through these third-party managers very long. I called hosting support, they said that they did not encounter this, they offered to talk with the operator providing Internet services. At the same time, a week ago everything worked quite quickly, the response was no more than 0.5 seconds. What are some ideas about this?