See Spaceinvader One's setup video here:
I wrote the template that pulls in the Official Docker Container from PiHole. I swapped over from my unofficial one a long time ago that that a fully supported version could be distributed. Make sure that your repository for pihole is = pihole/pihole:latest and not the old diginc repository.
If you use the latest tag, you should have v 4.0.0-1. The release tags are here: https://hub.docker.com/r/pihole/pihole/tags
how did you update? Was it the docker container or inside the docker container (which you shouldn't do)?.
My template pulls down the official docker container with no changes. If there are bugs with Pi-hole, please log them at https://github.com/pi-hole/pi-hole/issues or https://pi-hole.net/