Trouble (rlm_python) with grpcio.

Good day Team. Several days ago I tried to use grpc for authentication in the python3 module, but my request to the backend service failed. That was pretty strange and I spent some time troubleshooting the problem. First, all works well if I call script from *instantiate* section, but for case if i try use call for example in *authentication,* nothing happens (grpc constantly tries to reach backend service) and radiusd stops proceeding new authentication requests. I think there is some kind of threading issue of python. Currently I don't have a solution to this issue but maybe you can help with this. ps. Centos8.x , freerad 3.20, python 3.6 and grpcio 1.37 if i dont mind.