Hey @Elliot,
I see this issue is still in effect, as I’m experiencing it myself. Just to add on to the information already provided by everyone else. I’m using the JSON API plugin to use WordPress strictly as an admin/backend, which makes proper image attachment critical as there won’t be any actual connection between wordpress and my eventual front-end beyond the API call.
The steps to the bug remain:
1) Upload an Image when attaching to ACF field = OK
2) Upload an Image and THEN attach to ACF field = attachments field empty
Additionally, when you remove an image from a post, it does not remove the associated attachment information. So on an API call where we’re looking at the attachments, we’ll be seeing attachments that no longer exist.
