The Gantt chart is throwing the error: Cannot read properties of undefined (reading 'startDate').

[alex.l]

Sorry, I can't use your test case because access is blocked by someone else. Please let me know when it will be possible.

[mrefaat]

Please check now

[alex.l]

The error occurs when i specify:

timeRanges: {
                    showCurrentTimeLine: true
                },

and setting
weekStartDay : 0 for Sunday

Please try to remove data and see if error persists with showCurrentTimeLine and weekStartDay configured.
Try to apply data by parts and see what change will affect on the error.

I can't change your code, it makes debugging quite hard.