I use discord authentication oauth2 method, which basically returns to me the access + refresh tokens.
In the dev mode it worked perfectly fine for me, but in production it just stops working.
Each time I try and trigger that api endpoint and the return value differs from the previous one it insta deletes the access and refresh token cookies (at, rt).

This is how I store the cookies after I authenticated and it works perfectly fine:

    const response = NextResponse.json("http://localhost:3000/databases");

    const accessTokenCookie = serialize("at", accessToken, {
      httpOnly: true,
      secure: false,
      maxAge: 604800,
      sameSite: "strict",
      path: "/",
    });

    const refreshTokenCookie = serialize("rt", refreshToken, {
      httpOnly: true,
      secure: false,
      maxAge: tokenExpirySeconds,
      sameSite: "strict",
      path: "/",
    });

    response.headers.append("Set-Cookie", accessTokenCookie);
    response.headers.append("Set-Cookie", refreshTokenCookie);

    return response;

And this is the endpoint that screws the cookies:

import axios from "axios";
import { NextRequest, NextResponse } from "next/server";
import { RequestCookie } from "next/dist/compiled/@edge-runtime/cookies";
import db from "@/app/_utils/db";

export async function POST(req: NextRequest) {
  let body;
  try {
    body = await req.json();
  } catch (error) {
    return new NextResponse("Invalid request body", { status: 400 });
  }

  try {
    const {
      accessToken: accessTokenArgument,
      cookies: sentCookies,
    }: { accessToken: string; cookies: Record<string, RequestCookie> } = body;

    if (accessTokenArgument) {
      try {
        const UserData = (
          await axios.get("https://discord.com/api/users/@me", {
            headers: {
              Authorization: `Bearer ${accessTokenArgument}`,
            },
            withCredentials: true,
          })
        ).data;

        if (!UserData) {
          return new NextResponse("Failed to retrieve user's data", {
            status: 401,
          });
        }

        return NextResponse.json({ UserData }, { status: 200 });
      } catch (error) {
        return new NextResponse("Error retrieving user data", { status: 500 });
      }
    }
    let accessToken = sentCookies?.at?.value;

    if (!accessToken) {
      return NextResponse.json("No AT", { status: 500 });
    }
    try {
      const response = await axios.get("https://discord.com/api/users/@me", {
        headers: { Authorization: `Bearer ${accessToken}` },
        withCredentials: true,
      });

      const roles = await db.roles.findMany({
        where: { user_id: response.data.id },
        select: { role_name: true, color: true },
      });

      const { id, global_name, avatar } = response.data;

      const user = await db.users.findFirst({ where: { uid: id } });

      if (user) {
        await db.users.update({
          where: { uid: id },
          data: { username: global_name, avatar },
        });
      }

      const res = NextResponse.json(
        {
          UserData: response.data,
          roles,
          userPremium: user?.issubscribed,
        },
        { status: 200 }
      );

      return res;
    } catch (error) {
      return new NextResponse("Internal Server Error", { status: 500 });
    }
  } catch (err) {
    return new NextResponse("Internal Server Error", { status: 500 });
  }
}