I have attached a sample report definition with two Graphs using the same embedded data source. The first one has a DateTimeScale X-axis and looks like your first screenshot. The second graph has a CategoryScale X-axis and looks somehow like your second screenshot, however, the lineSeries are drawn over the barSeries, which is the expected behavior.
Can you send us a report definition that replicates the behavior of the second screenshot? For example, you may modify the attached sample.
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