ObservationPlanes show non-existing particles

This is a follow-up to the discussion on the slack development channel.

I've been simulating electromagnetic (1TeV initial electron) showers with the examples/corsika.cpp script. The only option I have changed is the emcut, which I changed to 20MeV.

If I look at the longitudinal profile (here for the charged particles), they look like this:

This means that I should expect zero particles on my observation plane. But if I look at the output from the ObservationPlane, I have 8931 entries in the parquet file! The energy distribution of these particles look like this:

Note that a lot of these particles have an energy very close to the cut energy, but not all of them.

For a 10 TeV shower, we would expect some charged particles according to the observation plane:

But the output of the observation plane shows 91676 particles!

This might, but doesn't have to be, related to issue #572.