@anon94532230 We’ve done some more digging on our end and came across this post from last year. It seemed promising - the error message mentioned in the title was the exact one we were seeing in our cloud environments.
We determined that this was an instance where one of our other dependencies was interfering with the openid-client dependency of forest-express.
The culprit in our case, which was google-auth-library. We found that we had a dependency using a version of google-auth-library earlier than v3.x. Upgrading this package to the point that it was using a 3.x version of google-auth-library seems like it is resolving our issues.
I don’t see any mention of the possibility that this can happen in the upgrade docs for v7, when this dependency was introduced. A note anywhere in this documentation that there are some known issues with other project dependencies causing these issues may have prevented us from running into this.