Yeah, it's really tricky to reset the defaults because you have to go so many different places to do that. There might be an easier solution, however, that is so obvious that naturally I didn't see it.

Either reset everything to the way it was or start a new map. Now *Right* click on the Floor button to get the floors Select Drawing Tool dialog box and select Floor, Tiles S Brown (S = small). It uses the exact same symbol/pattern, but at about 1/4 the size of the L Brown version, so it looks more like regular brick.

See if that works better for you.