(Solved) Problem with bar graph visualization of kWh/d

When trying to generate a 'kWh per day' bar graph from an incrementing kWh feed I get a strange result (interval set to 86400). The bars of every second Sunday are missing and the data looks quite different to the bar graph of 'real' kWh/d feed. Am I doing something wrong there?

I am using V8.3.5 here.

EDIT: Sorry, I just see that there are data points missing in the kWh feed for longer intervals because my server was down. I did not realize this earlier because you just see a straight line in the visualization where the data is missing (and no 'gap').