Display field collection items by using twig
That is not a good idea to use kint() to collect the values somewhere in #markupkeys or other render elements. You can get the values from the field object, which is in a field collection an entity which then refers to the children fields. But if you use field collection, you should try first to use the theming, that is provided by this module. That is configure the format of the field collection in ui and then look in twig debug for the templates that are used by doing this and modify them.