@dianedetoeuf Thanks for refreshing my memory on this 
The issue was (as you reported correctly in the other thread you linked to) that using this hack only made it look like the images were deleted. What it removed though was just the file name in the submission, which no longer showed the attachment in the data table or single submission view. It didn’t actually remove the attachment from your storage. That’s why some users noticed that images “deleted” this way would still appear in the gallery. We fixed this issue with a recent release, see Release Notes - version 2.023.48.
At the moment, the only available way for removing attachments is to delete submissions (single, bulk, or by removing the entire project). Once the bulk deletion feature is rolled out it will be possible to remove attachments for multiple submissions without deleting submissions.
