Investigate stale read on CreateElementChildren

Mentionned in https://redmine.teklia.com/issues/8645

Could be the root cause of a painful bug happening on Socface : https://redmine.teklia.com/issues/8478

It would seems possible, as the endpoint uses prod database with replica, and the error is indeed a 404.

MLProd people having issues to reproduce also smells of stale read, as it's more frequent when the system is under heavy load (ie socface process publication)