At first I thought that it was a permissions issue, but it looks like that there is no issue when saving of other data ...
Maybe, the problem occur during the cropping/resizing of the images, so you get a broken JSON Response.
PS. Take a look into the apache error log to see if IM submits any error messages.
Maybe, the problem occur during the cropping/resizing of the images, so you get a broken JSON Response.
PS. Take a look into the apache error log to see if IM submits any error messages.