1 GeV electron does not interact in Argon

Hi Everyone.

I am shooting many particles from the center of a gas Argon volume (cilinder r = 1m, l = 2) immersed in a magnetic field of 2T. Running many particles I observed that there are a couple of charged particles which do not make any steps in the detector.

For example one such particle is an electron having the following initial momenta components:
-0.407355 -0.941119 2.81729 | GeV/c

Even though I have a thin target at the middle of the detector (0.5cm radius/ 0.05mm width) I would have expected it to propagate in the detector given the momentum.

To double check, I simulate separately this electron and indeed it passes through the detector, making several steps.

Does anyone have any idea why when I simulate more events there are this kind of particle which don’t make any steps in the detector?