you're conveniently ignoring the bit about another client on the same system (incuding router and server) NOT disconnecting. How could that happen and it not be "Filezilla's fault?"
Because FileZilla does not disconnect either, it merely gets disconnected.
Simple car analogy: There's a huge difference between stealing a car and getting your car stolen.
So get your facts straight.
I don't believe I ever came in here bitching and assuming the program sucks. I came in for help...
Then please believe my explanation that either the server or some router or firewall disconnects you. FileZilla 3.x does things the right way, it works just fine with proper servers.
The only difference with FileZilla 3 and other clients is the usage of keepalive commands, which are just bandwidth hogs, they are not needed on proper servers, routers and firewalls. Fix your servers, routers and firewalls, I will not waste any effort with broken third party components.