Possable you have to adjsut the focus of the screen to the film plane. Not all screen mounts are the same but to check it is fairly simple. A plain GG has no glass or fesnell adn the split has. mounts were also changed over the years as well.
GG ont eh film gate wihtthe back open.. point the camera at a well lit target, focus the screen with a loupe. then check the GG onth efilm gate with the loupe.. if all is well.. enjoy your camera. If not then adjsutments are needed.
The 4 large screws with the spanner holes are the height adjsutments. Before you move or do anyting.. make a small scratch in each in reference to a screw or a stationary part of the body.
By lifting the screen to see if the height has to go up or down will determine which way the screws all get turned evenly the same amt. Check the GG often n make sure you are writing then how many tunrsthe screws got.. amazing how fast you can get confused.
If you are not comfortable doing this send the camera out for adjsutments.
This is a commong problem when using the brite screens then going back to the old style. .different thickness n variations change the focus.