Fred bought a Plume Mesh router to improve coverage in his house and improve the latency. But the latency problem is still there while doing file sharing. What else can he do to stop it? Leo says that he should look at DSLReports bandwidth tester. It'll give him an accurate measurement of his latency issues. He should also run speedtest.net.
The real culprit is probably that Fred is using satellite for his internet connection, which is also affecting his network. What Fred needs to do is share files on his own network, not on the public internet. He should change the settings in his router. Fred should be able to find a tutorial online to do this.