I would like to report that I’m experiencing the same issue. A front end ACF form is used to create a pending CPT and contains image fields. The uploaded images show up in the List view in Media Library but not in the Grid view. So they are successfully uploaded and for the most part very much the same as any other image – I’ve not been able to pinpoint the difference by looking in the database so far.
Unfortunately switching the uploader to the ‘WordPress’ media uploader isn’t a good solution for this site because we don’t want the users to be able to browse and select images that are already in the Media Library.
My client noticed it out for the same reason as OP’s client – they needed to add the image to another field. WordPress uses the Grid View for the Media Library that pops up when attaching images to fields or adding them to the WYSIWYG, so the images can’t be added to any other fields.
