Problem with Mass flow/particle flow

Hello. I am beginner with liggghts and try to learn some basics.

I try to measure Mass flow on pipe, but have problem with error:

i put particles in silo and then i open hatch, the measurement plane is same as hatch but with different name.

I will be very happy if someone can help me, or give some examples Thank you.

ERROR: Illegal variable command (/build/liggghts-YO7u74/liggghts-3.8.0+repack1/src/variable.cpp:418)
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Primary job terminated normally, but 1 process returned
a non-zero exit code. Per user-direction, the job has been aborted.
--------------------------------------------------------------------------

SIGINT/SIGTERM caught - Writing restart on next occasion and quitting after that.
--------------------------------------------------------------------------
mpirun detected that one or more processes exited with non-zero status, thus causing
the job to be terminated. The first process to do so was:

Process name: [[33368,1],4]
Exit code: 1