Hi Emrah,
Greetings from Syncfusion.
For your query, we would like to inform you that the behavior has changed in the latest version of the Gantt Chart. In the older version, the default taskType was "FixedWork," so the work value was displayed as provided in the data source without using taskType property.
In the latest version, we have changed the default taskType to "FixedUnit" As a result, due to internal calculations, the work property values in the data source are reset to 0 if no resource is assigned. To overcome this issue, we suggest setting the taskType to "FixedWork" in the Gantt Chart. Refer to the release notes' breaking changes for your reference.
Code-Snippet:
GanttComponent id="Editing" taskType='FixedWork' > </GanttComponent> |
Sample - Zbeelf (forked) - StackBlitz
Documentation - Work in React Gantt component | Syncfusion
Release notes - Essential Studio for React 2024 Volume 1 main Release Release Notes (syncfusion.com)

Regards,
Sridharan