Psychopy freezing

Psychopy version: standalone psychopy 2021.1.4
OS: windows 10 .
RAM: 8gb

I am running fMRI task such that player makes continuous movement using joystick where the location of player and computer agent is updated every frame. The duration of the task is about 20min.
I am running this experiment using Coder view only (not using Builder)
I frequently experienced freezing of experiment with message “python is not responding” in 50% of subjects at random timing (early or late).
There were no error message such as python coding error (neither in psychopy runner screen nor in log file)
I also monitored memory usage which seems to have no relationship with this freezing (no increase of memory usage at the freeze, psychopy used only 200mb of memory among 8gb) - so I don’t think that this is related to memory leak.

I would appreciate it if anyone have similar experience or if there are any suggestions.