NextAuth works on local dev but not on local prod

I am running into the issue where my Credentials Authentication flow works in development mode but when I build the app and start it on my local machine, the authentication does not work anymore. I have made sure that the environment variables are exactly the same - both dev and prod are talking to the same database. One thing to note: I am using a custom credentials auth flow, in which I am querying an Active Directoy (AD) via an LDAP client. I suspect that the issue is somewhere there, but the fact that it only occurs in prod makes it hard to debug.