I am having the same issue – original gallery showing with the Dynamic Gallery.
WP v4.7.5
WooCommerce v3.0.5
Thanks
@predatron and @nomadr
WooCommerce Dynamic Gallery when activated auto replaces the default WooCommerce Gallery – WC Dynamic Gallery is ON then it is auto – places the gallery in the same <div>
Perhaps the theme you are uses makes a custom code to make the gallery position and hides the default WooCommerce div?
If that was the case that would be why the default gallery (which is custom from theme or another plugin) is still showing and that WC Dynamic Gallery is showing where the default WC gallery should be.
That is all i can think would be the issue without being able to see it – its just a guess really until then.
If you like please confirm what theme you are using and post a link in your reply to a product page where I can see the issue.
Regards
Steve