I got this error setting up a multi-lingual link in simplytest.me
http://s91d379121030b06.s2.simplytest.me/node/add/article
Status message
Article test with link has been created.
Error message
Drupal\Core\Entity\EntityStorageException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '2e54f381-397f-4226-ae00-a9f7fd00ac18' for key 'uuid': INSERT INTO {node} (nid, uuid, vid, type, langcode, tnid, translate) VALUES (default, :db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5); Array ( [:db_insert_placeholder_0] => 2e54f381-397f-4226-ae00-a9f7fd00ac18 [:db_insert_placeholder_1] => [:db_insert_placeholder_2] => article [:db_insert_placeholder_3] => en [:db_insert_placeholder_4] => 0 [:db_insert_placeholder_5] => 0 ) in Drupal\Core\Entity\DatabaseStorageControllerNG->save() (line 404 of /home/s91d379121030b06/www/core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php).
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Closest I could find to related error was #1998658: Creating Custom Block with same name as existing block throws SQL error