We have analyzed the reported query and prepared the Gantt sample with MVC on server side.
And refreshed the Gantt on CRUD operations. We are unable to reproduce the reported issue. Please ensure whether valid ParentId/startDate/endDate is retrieved while refreshing Gantt after updating Database.
We have also prepared the sample for your reference. Please find the sample from below location
If still issue exists at your end please revert us by modifying the sample based on your application along with the replication procedure. This would be helpful for us to serve you.
Jone sherine P S