"500 OK" when using routeRules to external backend

Error fetching author data: FetchError: [GET] "/api/mc-services/litematica/profile/Molforte?lang=ru": 500 OK
    at async $fetchRaw2 (file:///www/website/node/server/chunks/nitro/nitro.mjs:3921:14)
    at async $fetch2 (file:///www/website/node/server/chunks/nitro/nitro.mjs:3926:15)
    at async setup (file:///www/website/node/server/chunks/build/index-D8Vo9RTZ.mjs:241:22) {
  statusCode: 500,
  fatal: false,
  unhandled: false,
  statusMessage: 'OK',
  data: {
    url: '/api/mc-services/litematica/profile/Molforte?lang=ru',
    statusCode: 500,
    statusMessage: '',
    message: 'internal server error',
    stack: ''
  },
  [cause]: FetchError: [GET] "/api/mc-services/litematica/profile/Molforte?lang=ru": 500 OK
      at async $fetchRaw2 (file:///www/website/node/server/chunks/nitro/nitro.mjs:3921:14)
      at async $fetch2 (file:///www/website/node/server/chunks/nitro/nitro.mjs:3926:15)
      at async setup (file:///www/website/node/server/chunks/build/index-D8Vo9RTZ.mjs:241:22)
}

// nuxt.config.ts
let isPrerender = false;
if (
  process.argv.find((arg) => arg.includes('/nuxi')) &&
  (process.argv.includes('build') || process.argv.includes('generate')) // nuxi build command
) {
  isPrerender = true;
}

  routeRules: {
    // '/api/search': {
    //   prerender: true,
    //   cache: {},
    // },
    '/api/**': {
      proxy:
        // process.env.NODE_ENV === 'development' ||
        isPrerender
          ? 'https://api.redenmc.com/api/**'
          : 'http://localhost:10005/api/**',
    },
  },