I ran into the same issue using that Helm chart. The issue for me was with the bundled Postgres bundled into the chart itself (ref:
https://github.com/bootc/netbox-chart/issues/164). The chart author is also openly asking for assistance with maintaining the chart (ref:
https://github.com/netbox-community/netbox-docker/discussions/1160)
While I have not tried it yet, my plan is to follow the recommended steps for production and install a dedicated Postgres instance that is >12 (meets Netbox 1.3.6 and 1.3.7 requirements), and adjust the chart YAML to point to the dedicated instance.
Again, I have not yet tried this, but I suspect that it will work.