MediaThumbnailFormatter produces unhelpful text alternative for image media items.

We have trouble with alt text for Thumbnail formatter. It is very similar to Media entity bug, but we use module Media in core.

In core/modules/media/src/Plugin/Field/FieldFormatter/MediaThumbnailFormatter.php is code

$media_items = $this->getEntitiesToView($items, $langcode);

I was inspect in Xdebug variable $items and I found, that there are using Thumbnail as alt ($items->list[0]->properties['entity']->target->entity->values['thumbnail']['x-default'])

I don't know, where is source of $items. How can I fix it?