Gromit is my favourite skin. I have always used it without a problem. However since about 2 months now whenever I rendered it (I use it as standalone on my website) I don't get the expected result. What happens is when I click on the thumbnail the picture is shown like for a nano-second in the expected format and then shrinks to a very small format. I have been using the same settings for ages. It is only since about 2 months that I get this reaction.
Please give us a link to your site. No one else has reported these kinds of symptoms. The skin is now fully responsive, but that should produce only the kind of resizing you see on my demo site, https://jgromit.com/gromit/
I have found where the problem lies. I always add a youtube embed code to the pictures page. Something like
<iframe width="560" height="315" src="https://www.youtube.com/embed/videoseries?list=UUljBfmJffQppZYiX2h3pgGQ" frameborder="0" allowfullscreen></iframe> that shows up on all the pages. This has never been a problem until a while ago. Now that I have removed that code everything is fine. I would still love to be able to embed videos though
Without seeing your site, I can only guess. But I suspect that what's happening is that when the slide page is displayed, the responsiveness script tries to display all of the page content, so that there are no vertical scrollbars. But the page content, in your case, also includes a fairly large iframe. So, the script tries to make the slide image small enough so that everything on the page "fits," and there's just too much material on the page. So, you end up with a relatively tiny slide image. (The same thing would happen if your comments under the slide image were twenty lines long, for example.)
Try using a different responsiveness mode for the slide pages. Under Gromit > Layout > Slides > Slide Page Responsiveness > Type, choose width instead of full.
There might be a way to get the benefit of full responsiveness, but still be able to show your embedded video below the slide image, but I'd have to see your page coding, and also have you explain how you're planting the video on each slide page, to know how best to do that. I can't do it "blind."
Thanks for your great help. I have made a test page at https://afropeans.com/test/ Gromit --> Setting--> Code--> Slide page--> HTML body closing that is where I put the embed and the statcounter codes.
Btw. If I do as you suggested and set the responsiveness to width instead of full the problem disappears. So I think I will just do that from now on.
For now, your best bet is to choose one of the other slide responsiveness modes - under Gromit > Layout > Slides > Slide Page Responsiveness > Type, try image or width. Either one will avoid the "shrinking image" phenomenon.