Yes, everything in initialized before WP does AJAX actions, so that eliminates a timing issue during save.
I honestly don’t see any reason there is an issue.
Going back to your code
update_field($key, $aa_winter_sports_point->properties->$value, $existing_aa_winter_sports_point->ID)
is it possible that $aa_winter_sports_point->properties->$value or $existing_aa_winter_sports_point->ID has an incorrect value.
