Is it just the upper left corner, or is it all of the top of the display?
It kind of looks like all rows at the bottom are too tall.
Maybe print a test pattern that displays every other character as something that takes up as much space as possible (ideally an inverted space character) and the other characters as blanks, filling the screen (except the lower right corner if printing there would cause the display to scroll), and take a photo of it.
Judging by what I see on your pictures it's a pure analogue issue in the CRT electronics. Reseating RAMs or whatnot will likely not do any difference.
Generic tip: Repair of the CRT electronics is usually more or less the same as repairing old CRT TVs so if you don't end up with any good advice here you might want to ask in some forum that is more about TVs (unless they don't want computer related stuff in their forum).