That doesn't answer the question. Can you not open it in Heidegger anymore? You can't open it in another editor?
Heidegger removes the "Read-Only" flag on the file even after it's done. If another editor is trying to forcibly turn it off when it already is off that may cause an error.
And no, there's not another monster attack editor. That's why I made Heidegger. You don't need a "better one" you just want Heidegger to work.