This is a silly issue, but it's the second time I've run into it so...
When I have my system font size cranked up to 144 dpi the installer window is so large on my screen that I can't access the buttons. This might just be an issue with my desktop environment (KDE Plasma). To recreate: Start Menu -> System Settings -> Font -> Click Force fonts DPI and change value to 144 -> run installer. On any normal monitor the buttons to advance will be off the screen.
(See this link for pictures/better instructions to change the font size.)
I've been flipping my monitor vertically to get at the buttons.
When I try to resize the window down, I think I hit the minimum size because it won't scrunch down to fit my screen.
Hope that's descriptive enough.