Line chart doesn't connect lines between data points

Hi Community

Does anybody know why the line chart doesn't show the lines from point to point properly?

My goal: Two lines in one chart where the lines are connected (including yellow lines in the picture)
At the moment, only two random points are connected. Points are visible.

Any hints are welcome.

Kibana v7.6.0

@fim dou you have any null values into your dataset? It looks like it can cause those problems.

Yes, indeed. There are null values in both of my data sets.
Thanks Tiago for your feedback.