When editing to [[index]] (which is my indexPage) and then running Sync: Space, there is an error: offline, and the JavaScript console says
but all other pages can sync well. I tried disabling space-lua, disabling plugs, and also resetClient=1 in the url, but none fixed the issue. I also tried restarting the server itself several times, but it didn't help. Haven't had the time to double check my systemd and nginx configs, but they have worked pretty well since day one.
In my index page there are just some queries. If I edit the index.md directly on my server though, this edit gets saved properly to all browser instances accessed later.