I just made an image 60k pixels high and when I went to save as, PDF wasn't an option so it does look like the height of the image is the problem.
I think most programs have a max size(2gb usually) or max width/height that they’re happy with. So I wouldn’t be surprised if the 60000 was doing it
There’s this thread about people who had big files too, and for them it was size—so they reduced the ppi.
