MD run failed(unstable simulation was killed, with unstable = NOT writing in log file for 60 sec)

[zdworld]

when running the optimization cycle 3， each step print an error info like:

Starting iteration 267 at 15:56:08 on 20-10-2023
  MD run failed (unstable simulation was killed, with unstable = NOT writing in log file for 60 sec)
  Iteration time: 8.73 min

but the log file is writed normally. md.log