BOA image field file path

upgrading from D6 (not BOA) to D7 (BOA)

My D7 BOA site has an image field which is stored in /files/my-image-field and shows in the database as /files/my-image-field/example.jpg

so the image path should be

example.com/files/my-image-field/example.jpg

but on the page the images do not load (404) because a horrible prefix has been added =

example.com/sites/example.com/files/files/my-image-field/example.jpg

I think this prefix comes from Public file system path in admin/config/media/file-system

so my question please - what should my public file system path be and can I make my image field path work as

example.com/files/my-image-field/example.jpg

or must it have some kind of prefix like

example.com/sites/example.com/files/files/my-image-field/example.jpg

If it must have a prefix then does that mean I need to rewrite all the paths for this field in my database ie to add the prefix?