Hi @megancm
Sorry to hear you are still having the issue. There is definitely a conflict in code happening, as the relationship field works fine on my install and all others that I know of.
Can you try changing $posts = get_field('store-type');
to $posts = get_field('store-type', false, false);
This will prevent any loading of actual posts and if this fixes the issue, then the issue must be a filter hooked into the pre_get_posts or similar.
Thanks
E