NestJS CORS Error It's working well all of a sudden, but an error suddenly occurs

Question

import { NestFactory, Reflector } from "@nestjs/core";
import { Logger, ValidationPipe } from "@nestjs/common";
import { AppModule } from "./app.module";
import { RolesGuard } from "./admin/role.guard";
import * as express from "express";
import { CustomIoAdapter } from "./custom.io.adapter";
import { readFileSync } from "fs";
import * as cors from 'cors';

async function bootstrap() {
  let app;

  if (process.env.NODE_ENV === "production") {
    console.debug("===== [main] 배포 환경에서 실행되는 로그 =====");
    Logger.overrideLogger(["log", "warn", "error"]);

    const keyPath = "/etc/letsencrypt/live/api.xn--oy2b11o0qft9m.com/privkey.pem";
    const certPath = "/etc/letsencrypt/live/api.xn--oy2b11o0qft9m.com/fullchain.pem";
    const httpsOptions = {
      key: readFileSync(keyPath),
      cert: readFileSync(certPath)
    };

    app = await NestFactory.create(AppModule, { httpsOptions });
  } else {
    console.debug("===== [main] 개발 환경에서 실행되는 로그 =====");
    app = await NestFactory.create(AppModule);
  }

  app.useGlobalPipes(
    new ValidationPipe({
      whitelist: true,
      forbidNonWhitelisted: true,
      transform: true
    })
  );

  process.env.TZ = "Asia/Seoul";

  app.use(cors({
    origin: '*',
    methods: 'GET,HEAD,PUT,PATCH,POST,DELETE',
    allowedHeaders: 'Content-Type, Accept',
    credentials: true,
  }));

  app.useGlobalGuards(new RolesGuard(new Reflector()));

  app.useWebSocketAdapter(new CustomIoAdapter(app));

  app.use("/uploads", express.static("uploads"));

  await app.listen(8000);
}

bootstrap();

22|nestjs-app  | TypeError: Invalid character in header content ["Access-Control-Allow-Origin"]
22|nestjs-app  |     at ServerResponse.setHeader (node:_http_outgoing:662:3)
22|nestjs-app  |     at applyHeaders (/root/seasonfree-backend/node_modules/cors/lib/index.js:153:15)
22|nestjs-app  |     at applyHeaders (/root/seasonfree-backend/node_modules/cors/lib/index.js:149:11)
22|nestjs-app  |     at applyHeaders (/root/seasonfree-backend/node_modules/cors/lib/index.js:149:11)
22|nestjs-app  |     at cors (/root/seasonfree-backend/node_modules/cors/lib/index.js:187:7)
22|nestjs-app  |     at /root/seasonfree-backend/node_modules/cors/lib/index.js:224:17
22|nestjs-app  |     at originCallback (/root/seasonfree-backend/node_modules/cors/lib/index.js:214:15)
22|nestjs-app  |     at /root/seasonfree-backend/node_modules/cors/lib/index.js:219:13
22|nestjs-app  |     at optionsCallback (/root/seasonfree-backend/node_modules/cors/lib/index.js:199:9)
22|nestjs-app  |     at Array.corsMiddleware (/root/seasonfree-backend/node_modules/cors/lib/index.js:204:7) {
22|nestjs-app  |   code: 'ERR_INVALID_CHAR'
22|nestjs-app  | }

After developing WAS using nestJS, I uploaded it to the server and used it well. However, I received a manager call today saying that there is an error all of a sudden. The React and Nest applications are currently running on one server, both of which will communicate through nginx. The following is the nginx configuration file.

[API NGINX]

server {
    listen 80;
    server_name api.xn--oy2b11o0qft9m.com;

    return 301 https://$host$request_uri;
}

server {
    listen 443 ssl;
    server_name api.xn--oy2b11o0qft9m.com;

    ssl_certificate /etc/letsencrypt/live/api.xn--oy2b11o0qft9m.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/api.xn--oy2b11o0qft9m.com/privkey.pem;

    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_prefer_server_ciphers on;
    ssl_ciphers HIGH:!aNULL:!MD5;

    location / {
    # Add CORS headers
        if ($request_method = 'OPTIONS') {
            add_header 'Access-Control-Allow-Origin' '*' always;
            add_header 'Access-Control-Allow-Methods' 'GET, POST, PATCH, OPTIONS, DELETE, PUT' always;
            add_header 'Access-Control-Allow-Headers' 'Authorization, Content-Type' always;
            add_header 'Access-Control-Max-Age' 86400 always;
            add_header 'Content-Length' 0;
            add_header 'Content-Type' 'text/plain charset=UTF-8';
            return 204;
        }

        proxy_pass https://127.0.0.1:8000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_connect_timeout 60s;
        proxy_read_timeout 60s;
        proxy_send_timeout 60s;

        # location 안에 넣어줘야함
        proxy_buffer_size          128k;
        proxy_buffers              4 256k;
        proxy_busy_buffers_size    256k;
    }

    location /socket.io/ {
    # Add CORS headers
        if ($request_method = 'OPTIONS') {
            add_header 'Access-Control-Allow-Origin' '*' always;
            add_header 'Access-Control-Allow-Methods' 'GET, POST, PATCH, OPTIONS, DELETE, PUT' always;
            add_header 'Access-Control-Allow-Headers' 'Authorization, Content-Type' always;
            add_header 'Access-Control-Max-Age' 86400 always;
            add_header 'Content-Length' 0;
            add_header 'Content-Type' 'text/plain charset=UTF-8';
            return 204;
        }

        proxy_pass https://127.0.0.1:8000/socket.io/;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_connect_timeout 60s;
        proxy_read_timeout 60s;
        proxy_send_timeout 60s;

    # location 안에 넣어줘야함
        proxy_buffer_size          128k;
        proxy_buffers              4 256k;
        proxy_busy_buffers_size    256k;
    }
}

[React NGINX]

server {
  listen 80;
  server_name xn--oy2b11o0qft9m.com;

  # HTTP 요청을 HTTPS로 리다이렉트
  return 301 https://$host$request_uri;
}

server {
  listen 443 ssl http2;
  server_name xn--oy2b11o0qft9m.com;

  # SSL 인증서 적용하기
  ssl_certificate /etc/letsencrypt/live/xn--oy2b11o0qft9m.com/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/xn--oy2b11o0qft9m.com/privkey.pem;

  location / {
    proxy_pass http://localhost:3000;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
  }
}

I've tried everything possible, like restarting the server, Googling, asking GPT, etc.