[Plugin: NextGEN Gallery] Thumbnail resizing not working

I’m using NextGen Gallery here: https://www.baelavay.com/wordpress/?p=1449
(right under Photography and Illustration).

I used to have the “Set fix dimension” in Thumbnail options UNchecked. Now with a new page design, I want to have fix dimension. So I checked the “Set fix dimension” in the Thumbnail options and exchanged the thumbnails.

If you look at the thumbnails images, you see that the source images all have 150x150px. Example: https://www.baelavay.com/wordpress/wp-content/gallery/illustration/thumbs/thumbs_dont-do-drugs.jpg

But on the page, the thumbnails are still not displayed with fix dimension. Those thumbs that used to be portrait are stretched now to fit the old dimensions…

What did I miss?

https://www.ads-software.com/extend/plugins/nextgen-gallery/