The question is not so much if you have enough physical ram but if your docker management tool has established resource limits for the containers. Oom killer will stop the process regardless of the fact that there is enough free memory if the container goes over its Ressource contraints.

https://stackoverflow.com/questions/42345235/how-to-specify-memory-cpu-limit-in-docker-compose-version-3

Journactl doesn't work in unRAID.

So do the journalctl -p 4 -b on the host self.