Reconnecting to a restarting server fails when Fabric API is installed on said server

[Scubakay]

Description

About a month ago I wrote a little mod that lets you reconnect to a server when it restarts. To connect I use the same code as ConnectScreen::connect, copied over to my own Reconnect class, but with some unnecessary stuff stipped from it. The reconnection attempts are triggered by registering an event with ClientPlayConnectionEvents.DISCONNECT. The event starts a timer that tries to reconnect every thirty seconds using this method:

private static void connect(final MinecraftClient client, final ServerAddress address, @Nullable final ServerInfo info) {
        AutoRelogClient.LOGGER.info(String.format("Trying to connect to server: %s (%s)", server.name, server.address));

        Screen screen = client.currentScreen;
        InetSocketAddress inetSocketAddress;
        if (connection != null) {
            connection.disconnect(Text.literal("Disconnecting before trying again"));
        }

        try {
            Optional<InetSocketAddress> optional = AllowedAddressResolver.DEFAULT.resolve(address).map(Address::getInetSocketAddress);

            if (optional.isEmpty()) {
                AutoRelogClient.LOGGER.info("Couldn't resolve server address");
                return;
            }

            inetSocketAddress = optional.get();
            connection = ClientConnection.connect(inetSocketAddress, client.options.shouldUseNativeTransport());
            connection.setPacketListener(new ClientLoginNetworkHandler(connection, client, info, screen, false, null, Reconnect::setStatus));
            connection.send(new HandshakeC2SPacket(inetSocketAddress.getHostName(), inetSocketAddress.getPort(), NetworkState.LOGIN));
            connection.send(new LoginHelloC2SPacket(client.getSession().getUsername(), Optional.ofNullable(client.getSession().getUuidOrNull())));
        } catch (Exception exception) {
            AutoRelogClient.LOGGER.info(String.format("Couldn't connect to server: %s", exception.getCause()));
        }
    }

Now the weirdest thing is happening. This works fine with a vanilla server. It works fine with a Fabric server. But as soon as I install Fabric API on the server it stops working... When I wrote it I was dumbfounded, and now getting back to it after finally having some time to work on it again, I still am. ClientPlayConnectionEvents.JOIN is never called (this would cancel the timer to stop reconnection attempts). Now it just keeps looping and it's stuck on the Disconnect screen.

Logs don't seem to show much of interest. This is the server log:

[11:36:02] [Server thread/INFO]: com.mojang.authlib.GameProfile@6b7a761f[id=myguid,name=ScubaKay,properties={textures=[com.mojang.authlib.properties.Property@3217e9c4]},legacy=false] (/127.0.0.1:52070) lost connection: Disconnected
[11:36:02] [Server thread/WARN]: handleDisconnection() called twice

And this is the client log:

[11:42:32] [Netty Client IO #3/INFO] (autorelog) Auto relogging in 30 seconds
[11:43:02] [Timer-2/INFO] (autorelog) Trying to connect to server: Minecraft Server (localhost)
[11:43:02] [Netty Client IO #4/INFO] (autorelog) Logging in...
[11:43:03] [Downloader 0/INFO] (autorelog) Encrypting...
[11:43:04] [Netty Client IO #4/INFO] (autorelog) Negotiating...

What could be the reason for this ceasing to work when Fabric API is installed on the server?

Here's my repo btw: https://github.com/Scubakay/autorelog/blob/master/src/main/java/com/scubakay/autorelog/util/Reconnect.java