I am using Geant18.104.22.168 on Linux Ubuntu 20.04.2.
If I launch electrons (in a vacuum) at a surface then I can see that they stop at the first surface by debugging with gdb and stepping through PostStepDoIt and AlongStepDoIt.
However, if I detect the electrons and store the trajectory information in a file and then launch the electrons again from that file, I find the electrons do not stop at the first boundary, but they will stop at that boundary if they are backscattered. The electrons behave as if I launched them from inside the material. The boundary process is started, seemingly in the same way, in both cases. Can someone suggest a possible cause or maybe something I should be checking when debugging ?