Hi,
Thank you for the details! I have tried to log-in to check, but I am getting the following error: https://i.imgur.com/zOMsrDH.png
Error 504 usually means that there is either a firewall blocking a request, or the server cannot handle the request. If you have a lot of heavy duty plugins active, then it could very well cause this problem. I suggest disabling a few plugins (like 5 or more), to see if it changes anything – if so, then the server might be running out of either memory or processing power.