Yeah I use iOS. I changed now the ip in the router and set it to a fixed ip. Let’s see if this fixes something. Do you have any other suggestions?
Edit: see here this is a possible solution: NSURLErrorDomain - 1004 - #29 by MrNickIE
But for me this is not clear I use a Wireguard vpn for accessing my instance. The issue is the same if I use my local WiFi. I have to figure it out.
EDIT 2: Also Mobile Data has this feature, so it might be a good try to disable it.