Hi,

To reproduce the issue is easy:

• You need 2 servers with different IPs address (1 for the BO, 1 for the FO) . In front of them a LB (haproxy or whatever else)
• If you try to preview a Page, you will have an infinite loading (the page will never be display and you could have an http error in the network tools)

Digging into the source code, the problem comes from:
`vendor/ezsystems/ezplatform-page-builder/src/lib/Security/EditorialMode/TokenManager.php` line 92

if (!isset($payload['ip']) || $payload['ip'] !== $request->getClientIp()) {
    return false;
}

if you replace this code, the preview works has expected.
Idea: it could be nice to have a configuration to set ip address (like a trusted Proxies configuration)