Q:

Replace file button missing

I am missing a button to press when replacing a file.
Go to admin/content/file and edit a file.
For example: i am on file 778 at /file/778/edit

If you look at the Replace File field, there is no Replace/Upload button! So, yes, I can only upload an image but not replace the image.

A:

The actual replacement does not happen until you save the entity. There is no fancy AJAX-based form manipulation here (unlike a core file field), so there is no specific "upload" button attached to that "replace file" field.
You just need to specify your replacement file (populate that field) and then save the full form ("Save" button at the bottom) for the replacement to happen.

