"Oops! We've encountered an error." on orders endpoint

We are getting very slow responses and this for the /orders endpoint:

object(stdClass)#31 (3) {
  ["success"]=>
  bool(false)
  ["errors"]=>
  array(1) {
    [0]=>
    string(33) "Oops! We've encountered an error."
  }
  ["results"]=>
  array(0) {
  }
}

This is occurring even on orders that I have fetched many times before. The exact same API call that returned order info is now returning this error.