First, can you please stop saying that I am not helping you?
The whole world can see that I am doing everything possible to find a solution for you. Even then you are being very rude and unappreciative.
Just because you paid for my software does not mean that you can treat me like dirt. Please show some respect.
Also, I have to say this again, there is nothing wrong with the software. No where in the HTML specification does it say that thumnails need to be a specific size.
The 'best practice' rating in Lighthouse is just a recommendation. It will not make you website faster, as matter of fact using larger thumbnails will make your website slower because larger image take longer to load!
And even if the thumbnail option did not comply to the HTML specification then you can always set use custom thumbnail images yourself or use the 'Picture' object to set different images for different devices (also known as srcset).
I dare you to find other web deisgn software that even has these options...
But anyway, in the last few days I have repeatedly asked you to share a demo project with the problematic pages.
Until now you have shared 2 pages. Both of these pages now have a 100% score.
Doesn't that mean anything to you? Doesn't that prove that it can work and that I do have best intentions to help you?
Did you ever had a software product updated especially for you within a few hours after you asked for help?
The messages in Lighthouse are related to size of the thumbnails so we need to find the optimal scaling factor to make it work for all your images.
Based on the published page it looks like this gallery is using different spacing between the images so that may be part of the problem. I can only investigate this if I have the project file with that page.
There may be something difference in the way you have set up the images for this page:
https://freeclassicimages.com/Fantasy-Art-6.html
If you need further assistance then please share that page in a project so I can look at it.