This problem didn’t occured previously but seems to be effective now with some precise pictures I use for galleries such as cards and panorama, but mainly panoramas. But this is a random problem.
I tried to change size of the pics but problem remained. And I do not want my panorama pics will have less than 1024 pixels width.
Well, as the pics are well stored in the galleries, I create manually the problematic thumbnails cause I do not want to waste time or to adapt my picture size to a software problem and I upload them and that’s all !
I think this is the lonely solution I found to solve a specific problem which occured only one time, during the thumbnails creation. I have my thumbnail however the size of the pic to display.
Thanks for your response.
My galleries are presented here (still under construction) : https://www.shabbat-goy.com