Make sure that you’re actually just getting image ids with this: $image_ids = get_field('imggal', false, false);
Also, does it work with the limit plugin deactivated? Maybe it also limits images to those uploaded to the post.
In the end it seems more like an issue/bug with the gallery shortcode in WordPress than ACF. If you truly are getting all 6 attachment IDs with the above code ACF is doing it’s part correctly.
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