Minecraft Bungeecord: Connection closed after joining?

Hi, I recently started a Minecraft Bungeecord network. But whenever players join, they are kicked again immediately on the grounds that "An existing connection was closed under software control" or "An existing connection was closed by the remote host". I have already tried everything, deleted and redone Bungeecord Config, deleted ViaVersion and other Pligons and tried again, but the problem is still not solved. In case it is important, Bungeecord runs on 1.12.2.

If I and my friends (who all have rights to both Spirit and Bungeecord) join, the problem doesn't come immediately, but sometimes after a few minutes we're kicked too.

Try setting "ip_forwarding:" to true in the BungeeCord Config. Then in the spigot.yml set "bungeecord:" to true and in the server.properties onlinemode to false if you don't already have it.

Maybe it helps.

I'll give it a try, I'll write here whether it worked or not

So I have now set Bungeecord to true in spigot.yml, set Bungeecord IP forwarding to True in config, but when I join the error message "If you wish to use IP forwarding, please enable it in your Bungeecord Config as well "

Did not work