Next.js / @auth0/nextjs-auth0: “ERR_JWE_DECRYPTION_FAILED” Error

[OLT2000]

I have a Next.js (React) application that uses @auth0/nextjs-auth0 for authentication, deployed via Azure App Service and containers (Docker). As of last night or this morning, I can no longer access my application due to server-side errors relating to JWE decryption and auth0 secrets. What's extremely strange is this error only surfaced last night, despite not swapping my main slot into production for 2 weeks.

Context

• Framework: Next.js using the new App Router (13+) and @auth0/nextjs-auth0 (auth library).
• Auth Provider: Okta (the user sees the Okta login screen, then gets redirected back to /auth/callback).

Azure Setup:

• Each branch (Dev, Staging, Main) has its own App Service/deployment slot.
• Production and “prod-like” run the same code from the main branch; I use slot swaps to move changes in.
• The container is built and pushed to Azure Container Registry, then deployed to the App Service.

Auth0 FrontEnd Set Up:

import { Auth0Client } from "@auth0/nextjs-auth0/server";
import { NextResponse } from "next/server";

export const auth0 = new Auth0Client({
    authorizationParameters: {
        audience: process.env.API_BASE_URL,
        scope: 'openid profile email',
    },
    onCallback: async (error, context) => {
        if (error) {
            return NextResponse.redirect(
                new URL(`/error?error=${error.message}`, process.env.APP_BASE_URL)
            )
        }

        return NextResponse.redirect(
            new URL(context.returnTo || "/", process.env.APP_BASE_URL)
        )
    },
});

The Errors

• Only in the prod-like environment, right after a successful login, the user fails to be redirected to the dashboard. I see errors like:

Error: An error occurred in the Server Components render ...
ERR_JWE_DECRYPTION_FAILED at <anonymous> (/usr/src/.next/server/chunks/603.js:2:93746)

or

TypeError: "ikm"" must be an instance of Uint8Array or a string
    at nf (/usr/src/.next/server/chunks/987.js:27:305059)

I’ve running this in an incognito window to see if Cookies had expired. It was still broken.

Thank you! Any guidance or pointers would be extremely helpful.