There is a bug in the listings uploading the screenshots that causes the screenshots to be uploaded multiple times: https://snapcraft.io/waiterio-restaurant-pos
Please file an issue at https://github.com/canonical-websites/snapcraft.io/issues
Thanks for bringing this to our attention @giorgiozamparelli.
We filed a bug about this issue in our repo. You can keep track of progress here: https://github.com/canonical-websites/snapcraft.io/issues/1526. We promise to resolve it promptly
Sorry for not posting it directly on Github Issues. Thank you @pheurton for moving the problem to Github Issues!