In fact the problem is solved. After moving a test site using theme Unwise together with Nextgen Plus to the real domain i installed the Yoast SEO plugin. Unlucky all gallery pages (30 pieces) stopped showing images. Took me some time to found out. After deactivating Yoast all works fine again. I will try another plugin :-)
Yoast Seo
By Edwin Schlichter, 7 years ago.
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