The error file contains the following message. What does this mean and can I ignore it?
Geofar: Particle in region 3 (cell # 0) in position 1.000000000E+00
0.000000000E+00 1.000000000E+00
is now causing trouble, requesting a step of 6.258867675E-07 cm
to direction -2.285059979E-01 -9.412338141E-01 2.487245789E-01, error count: 0
[...skipped...]
Particle index 3 total energy 5.189748600E-04 GeV Nsurf 0
We succeeded in saving the particle: current region is n. 2 (cell # 0)
The message indicates a real problem if repeated more than a few times. As can be seen, the program has some difficulty to track a particle in a certain direction, and it tries to fix the problem by “nudging” the particle by a small amount, in case the problem is due to a rounding error near a boundary. If the message appears often, it is recommended to run the geometry debugger centering around the position reported in order to find if there is an error in the geometry description.