Log in with an account having circulate_remaining_permissions and staffaccess.
Find a patron with image. Try to check out for this patron.
Patron image is not loaded and when you give barcode to check out, you are disconnected from Koha.
Give borrowers permission to your account.
Try to checkout for the same patron as before. Patron image is correctly displaid and check out is done correctly.
This is because to display patron info, koha/members/patronimage.pl is called that needs borrowers permission.
This is a problem when you want an account only for circulation and not patron modification.
*** This bug has been marked as a duplicate of bug 17423 ***