You can check the max image height
setting and put the max value (2000000000), I believe it will fix this when you rebuild the html of the post
If you don’t have lightbox, you might try some css, something like this might work:
#reply-control .d-editor-preview img:not(.thumbnail):not(.ytp-thumbnail-image), .cooked img:not(.thumbnail):not(.ytp-thumbnail-image) {
max-width: 670px;
max-height: 2000000px;
}