Wrong offset from y-axis

Dear All,

I'm trying to use oxyplot to render a chart with lineseries.
I have added multiple lineseries to the chart but I seem to be having problems with the rendering.
In the added image the orange line should only begin after a certain time (not when the blue line starts).

points are being added in the following way:

 lineSeries1.Points.Add(new DataPoint(Offset, double.Parse(valueString)));

Is there a reason for this behavior?

https://onedrive.live.com/redir?resid=48B06587F86038FF!671&authkey=!AJcenx-Usfl9MAE&ithint=folder%2c.png


thanks for the help,

kr,

Robin