Filling a linechart with data (forecast) and then adding actual values clears the forecast values after some messages

[whyme12]

What are the steps to reproduce?

See attached file with an example flow.
The button "press first" injects forecast data.
The button "press multiple times" injects random values.
example_flow.json

Sometimes after the first press, sometimes after multiple presses, the forecast data gets deleted and only the random values persists.

Not sure if this is a bug or intended or if I did something wrong here.
I tried multiple versions, without topic, same topic, different topic, nothing seams to change the behaviour.

What happens?

I pull PV forecast data from https://forecast.solar/ and add the forecast values to a line chart.
Then when my inverter reports production, I want to add those values to the same chart.
Adding the production values works only for a few messages, then the forecast Data gets deleted.

Here are some screenshots. As you can see, the green data is the injected random value.

After another button press, the forecast data is gone and only the green data is visible.

What do you expect to happen?

I would expect that the forecast data will persist and does not get deleted after some new data gets added.

Please tell us about your environment:

• Node-RED-Dashboard version: 3.6.5
• Node-RED version: 3.1.8
• node.js version: v16.20.2
• npm version: 8.19.4
• Platform/OS: x86_64 Ubuntu Server with Docker
• Browser: Edge