Page cut off in vertical split screen

I’ve been using Scrivener for years without any problems, but yesterday I noticed that the text is getting cut off in the story I am writing. I can still type, but it doesn’t show on the screen. This problem only occurs in vertical split screen mode - horizontal split screen and full screen mode work fine. I tried closing and reopening the program, then I tried copying and pasting the entire document into another folder, but nothing works. Is there any solution to this? I can continue working using the other viewing modes, but vertical split screen is my favourite.