For line charts, we currently only handle events from one ItemStream, we will only use one of them (See ItemChart.updateLineChart and DataPageToolkit.addEndTimeLines, notice the use of only the first value from next()....)
This means we will only use events from one type, and possibly only part of the events of that type if they are parsed into different EventArrays, which will likely happen if the types have a duration.

For our handmade pages we know that types we line chart only suitable types, so we are quite safe there, but we might be able to be even safer, hence this bug.
For our generic pages, we will try to work around this in JMC-4499.