Since you already have FileZilla in place, and over the years it has been a very functional and relatively easy to use program, it makes sense to see if they have solved the problem you are facing.

I hunted through my backlog of downloads and installed programs; I no longer had FileZilla installed, and when I went searching there was one suspiciously labeled "sponsored" that Malwarebytes jumped on and quarantined. I found the most recent download (from 2016) and installed it and that triggered the update to the newest FileZilla.

To everyone else considering whether they want to install it themselves, I've saved you the trouble. When you open FileZilla there is a popup window with links to the Wiki and other sources of information. To figure out how to use it with your altered Network Solutions protocols, I suggest you search the Forums and read the page on Network Configuration. For in depth information they point you to this page. Scroll to the bottom of the page to find links to other specifications. The SFTP specifications page is a bunch of links that might help. It's a rabbit hole, but one you'll want to learn about if you want to keep your site up and running.