Ok,
Let’s go back to the Heroku H12 errors then.
I am trying to find what could generate such errors on your admin backend. Here are a few links for ideas:
Do you know which NodeJS version you use on your local machine and on your production server?
It could be the origin of the issue according to the last link.
There is a known issue with node.js 14.0.0 and above which requires pg package version 8.0.3 or higher in order to connect correctly to a postgres database and not timeout. Unless you are explicitly specifying a package dependency for the pg package,