Thumbnails Not Properly Displaying Throughout

Good morning,

I have been trying to solve this problem for a long time and just cant seem to figure it out.

I firstly thank you for your time. Here we go.

I updated my wordpress and website a month or so ago and upon completing the update I was seeing some drastic changes on my site that were not intended. Since then, I have manage to resolve most of the issues, but one that still plagues me is that my Thumbnails are not consistenty displaying throughout the site.

I have no means of reaching the theme creator and am not uber-familiar with the inner workings of wordpress. From what I understand, people have mentioned to me that it must be a theme override that is causing the issues.

Unfortunately, I do not know how to locate, edit or change this particular theme override and want to avoid causing any other issues.

I would appreciate if someone could take a look at these links:
-https://www.devronltd.com/product-category/construction/
-https://www.devronltd.com/product/green-living-fence/
-https://www.devronltd.com/product-category/green-living-fences/

Notice how all three thumbnails are displayed differently? (Related products, product page and category page)

Is there a way to make all thumbnails consistent? A code I can add? Or is there a way to locate the problem code that is causing the issue? Please let me know if you need more information.

Thanks in advance for any help, it is very much appreciated

Brandon

The page I need help with: [log in to see the link]