Scale not working when exporting

I am trying to edit the scale field while exporting an SVG, but two strange things occur. First, when I start typing to change the value, it might type the first character, but it won't type any more. It will go blank. It seems to particularly dislike deletion. Then, if I close the export dialog box and reopen it, the scale field is greyed out, and it won't accept any input. GIFs are attached.