The button is invisible and only when you click it you can see the red border, there is a chance that some computers run the game in faster speed which makes the border disappear faster than it should, in which case you have to quickly click 5 times on the corner and maybe that will fix the issue.
If this does not fix the problem I can only redirect to another site where it will be a separate save. https://www.newgrounds.com/portal/view/855208