On Sunday I tried to use the webui and log in, and get error 503 (nginx) and couldnt access the server. Early on Tuesday it vanished and I could do stuff on the server again, But today the error reappeared, and then a few hours later, vanished. How do I stop this happening? If you give any help, bare in mind I don't know how to do anything on the OS (but do pick up things quickly), so you'll need to give step-by-step instructions.