Solver crashed due to "Index out of bounds"

[R0ckySu]

[I 11:53:51.490 NotebookApp] Adapting from protocol version 5.1 (kernel 2be09a0b-a9dc-4ddf-9a93-8674ecb767e2) to 5.3 (client).

error: Mat::operator(): index out of bounds

error: Mat::operator(): index out of bounds
terminate called after throwing an instance of 'std::logic_error'
terminate called after throwing an instance of 'std::logic_error'
  what():  Mat::operator(): index out of bounds
  what():  Mat::operator(): index out of bounds

Solver crashed very frequently when I was trying to run the example_simple.py in Jupyter-notebook.

Environment:
macOS 10.15
python3.7
DM_solver was compiled by gcc-9

update: Crash only happens when the simulation steps exceeding 1000.