Why doesn't Bitrix AJAX work?

Question

1C-Bitrix

$APPLICATION->ShowHead();
CJSCore::Init();
$APPLICATION->IncludeComponent(
  "bitrix:news",
  "",
  [
    "AJAX_MODE" => "Y",
    "AJAX_OPTION_ADDITIONAL" => "",
    "AJAX_OPTION_HISTORY" => "Y",
    "AJAX_OPTION_JUMP" => "N",
    "AJAX_OPTION_STYLE" => "N",
    // ... и другие параметры вызова компонента
  ],
  false
);

The AJAX extension of the Bitrix JS library does not work (missing ). The site is multi-site. The Russian site is in the root, while the English site is in /en . Interestingly, the problem manifests itself only on hosting. It is even more interesting that AJAX does NOT work only if the php file with the bitrix:news complex component call and AJAX_MODE enabled is NOT located in the Russian site folder ( / ), but in the English site folder ( /en ). I tried to move this php file with a call to the bitrix:news complex component and enabled AJAX_MODE one level higher to the folder of the Russian-language site ( / ), without changing it. AJAX works.$arParams["AJAX_ID"]

I made a backup and deployed it to BitrixVM. In this case, I can’t repeat the problem - AJAX works, and all links encountered inside the component are converted into AJAX calls. On BitrixVM, I can only reproduce the issue with SEF_MODE enabled.
I got around the problem by setting up the routing (in urlrewrite.php):

$arUrlRewrite = [
 [
   'CONDITION' => '#^/en/folder/#',
   'PATH' => '/folder_en/index.php',
 ],
];

As you can see, now the php file with the bitrix:news complex component call and AJAX_MODE enabled ( /folder_en/index.php ) is now physically located not in /en , but in the root ( / ). Thus everything works!
But the problem is not solved. Maybe there are at least suggestions in which direction to dig?