This seems to be an issue at window creation time.
Occasionally I need 3 or 4 new windows to work with. I simply go to an existing nedit window and
type the "new window" accelerator 3 or 4 times. I've noticed that sometimes I get text in the window.
After looking into it I found that it's the actual text of my accelerator. I can duplicate it with any accelerator
on multiple platforms. It's somewhat timing sensitive, but very reproducible.
Just type any accelerator as the window is being created. It may take a few tries.