Gateway Timout after one minute

[FabianSer]

Hi, when I want to synchronize my Synology Carddav I get a gateway timout after exactly 1 minute.

CalDavSynchronizer.DataAccess.WebDavClientException: Response status code does not indicate success: '504' ('Gateway Time-out'). Message:
(...)
/* Copyright (c) 2022 Synology Inc. All rights reserved. */
(function(){var a={en:"Sorry, the page you are looking for is not found."
(...)

My DAV URL looks like this: http://Synology-IP:5050/carddav/Username/carddav-address/

In the synchronization profile, the test connection works after a few seconds, so the server should have reponded within a minute. No matter what I set as server timout in the general settings (currently 600 seconds), I get the gateway timeout after one minute.

Does anyone here have a solution for the issue?