I have reported this possibly conflict/bug between and/or standalone between GeneratePress and FV Flowplayer Video Player
By FolioVision. In FV I have a video poster .jpg set, whenever I work on a page with one of its videos, it adds it automatically as the featured image for that page and inserts the photo on the front and back end. I remove it, resave and it comes back, leaving a “new image” with a whateverimagename-1, whateverimagename-2, number after the newly/again created image.
Just thought I should bring to someone’s attention.