Handling Issues in Migration

Fix "non-existent config entity name returned by FieldStorageConfigInterface::getBundles()" Normally it will show that a field belongs to a non existing bundle for a node, comment etcetra in log post migration. Solving a field that does not belong to non existent bundle in a node, example, field_agenda present in a non existent bundle makemeeting of node type $key_value_factory = \Drupal::service("keyvalue");
$field_map_kv_store = $key_value_factory->get("entity.definitions.bundle_field_map");
$node_map = $field_map_kv_store->get("node");
print_r($node_map["field_agenda"]);
unset($node_map["field_agenda"]["bundles"]["makemeeting"]); // Removes the bundle mapped to the field
$field_map_kv_store->set("node", $node_map); // Updates Node Map
print_r($node_map["field_agenda"]);
Removing comment_body present in a non existent bundle comment_node_employee_recruitment, comment_node_newsletter_subscription, comment_node_blood_bank_interaction of comment type $key_value_factory = \Drupal::service("keyvalue");
$field_map_kv_store = $key_value_factory->get("entity.definitions.bundle_field_map");
$node_map = $field_map_kv_store->get("comment");
print_r($node_map["comment_body"]);
unset($node_map["comment_body"]["bundles"]["comment_node_employee_recruitment"]);
unset($node_map["comment_body"]["bundles"]["comment_node_newsletter_subscription"]);
unset($node_map["comment_body"]["bundles"]["comment_node_blood_bank_interaction"]);
$field_map_kv_store->set("comment", $node_map);
print_r($node_map["comment_body"]);
-- https://www.drupal.org/project/drupal/issues/2916266#comment-12301574 https://www.previousnext.com.au/blog/update-drupal-core-84-step-by-step-guide