I have a variation on your problem. My site was created just before your comments. I used vertical images on a six image plus description page (https://preservevistoso.org/our-board-your-neighbor). It displayed well on both PCs and phones. One of the photos needed to be changed a few weeks ago and that went without a hitch. I had to substitute another image today, and when I opened the editor, all the previous vertical images on the PC page had reverted to horizontal with no action on my part and cropped to the point of being unusable while the phone pics stayed OK and as-is. I dared not save the result. Lots of luck.
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