Thank you for the explication.
I’ve also seen that get_field('field')['subfield']
does not work very well when working with an image subfield in a custom block. get_field('field_subfield')
works!
For example:
$groupA_image = get_field( 'groupA')['img'];
$groupA_imgUrl = $groupA_image[ 'sizes' ][ 'large' ];
vs
$groupA_image = get_field( 'groupA_img' );
$groupA_imgUrl = $groupA_image[ 'sizes' ][ 'large' ];