I have a sample to reproduce the issue now but here is a description.

In the sample I add 2 stepline series. Both start at the exact same time but one has twice the number of points (and therefore is twice the timespan). Once added to the series, if you zoom in to the beginning point it appears that on series begin slightly after the other even though they both start at the same time. What I have found is that as the difference in two series' time spans increase that shift in the beginning increases as well.

The sample was too big to include the infragisitcs dlls I am using so I had to remove them. The version I am using is 10.3.20103.2021.

To reproduce the issue, run the sample, select the "Historical" radio button at the bottom left and then zoom in to the beginning. As you get closer to the 1 second interval level you will see the bottom series start to shift to the right a bit.