I'm going to resurrect this thread, because I've seen the same thing happen, even with the latest release.
I can confirm that the problem is Windows 10's display scaling. On my brand-new PC, the Windows setting for scaling (Settings/System/Display, "Change the size of text, apps, and other items") was set to 150%. This was on a Lenovo IdeaCentre, I don't know how other manufacturers might set it.
Now, 150% makes things much easier to read on a TV from across the room, but it definitely wreaks havoc with some apps' dialogs... in this case, the MC TV Setup dialog definitely gets cut off at the bottom. The only way to get at the Back/Next/Cancel buttons is to set the Windows Taskbar to auto-hide.
Having said that Windows is the problem, though: it doesn't help that TV Setup has a God-awful amount of empty space between the lowermost actual item in the dialog and the bottom of the window. Seriously, half the window is blank space! Yes, different stages of the wizard show more or less information in the window, but none of them use ALL of that space. If you folks at JR could remove all that blank area, you could shrink the window so it would fit on the screen no matter what the scaling was set to...