The same data, some of Gantt’s work does not work

Gantt chart using vue。
The data for each request is the same. Why is the Gantt chart displayed sometimes, and sometimes it is not displayed?
The picture on the left is the one that can show the right side of the Gantt chart.

Looks like the data at the left side and at the right side is valid and it differs a little. I see that there is durtion parameter. Gantt doesn’t count it as duration, but it’s not a problem as there is correct duration parameter.
It is not necessary related to data, maybe Gantt is not displayed because of something else.
If you can reproduce the issue in the following snippet, please click on the “Share” button and send me the link:
Or you can send me full vue.js package and I will try to see what might be wrong.