With a field like this:
{content_module module=ECB2 field=group block=dividers assign=dividers
tab='Dividers'
  sub1_field=file_picker sub1_name=image sub1_label='Image' sub1_top='images' }

When you create the first item, the filepicker goes to the defined folder
(uploads/images) and you can select the file. When you add an additional item,
the filepicker goes to the root /uploads/ folder. You can navigate to images and
select an image, but the thumbnail will be broken and the path will be incorrect
in the template output.

The workaround is to submit the page after creating each item, then reopen to
add the next one.