Editing form results adds new results
Editing a form result (implemented using EditExistingResult) results in adding new results to the form. This is a recent bug, I guess introduced somewhere in the last 6 months. I think it worked correctly in 4.30-dev, but it doesn't in 4.31.2.
Anyway, to reproduce, refer to the attached module (zip) + site (wharchive). After installing both you should be able to create a new result from the form page. Set the text and file field and submit. After that, the home page of the site shows the result with an edit link. Click the result to edit, submit, refresh, and you'll probably see 2 results instead of the expected 1.
A related problem seems to be that files (upload, images, canvas, etc) don't work properly anymore, so I've added a file field to the test form.