When using scale instead of aspect ratio images currently use the smallest srcset width for the height attribute on the image tag.
$elements[$delta]['#item_attributes']->setAttribute('width', $elements[$delta]['#srcset'][0]['width']);
$elements[$delta]['#item_attributes']->setAttribute('height', $elements[$delta]['#srcset'][0]['width']);
This gets corrected as soon as the javascript kicks in or the image loads and the intrinsic size takes over. This can cause a layout shift.
Render any image that has a height that's not equal to its width using 'scale'.
Check the width and height attributes in the page source.
Or open dev tools and throttle the network so you can see the dimensions shifting.
Calculate the correct height based on the image's aspect ratio.
Fixed
1.3
Code
Issue #3393306 by kubrick, seanB: Set correct initial height on scaled...
Automatically closed - issue fixed for 2 weeks with no activity.