JoinNode is destroying values



I have a simple measurement in stream:
The other is cpu measurement. When I join two nodes I am loosing my values except one value.

// Dataframe
var data = stream
    |eval(lambda: 100.0 - "m1.usage_idle")

So the JoinNode is destroying my values, only one value left from random host. How can I join my cpu metrics and my simple custom measurement AND save all values from all hosts I have in this stream?