Bug when sending messages

I found a small but very annoying bug that has been occurring when i attempt to send a message to multiple people at once.
I write in the players i send the message to and click the send button, but once i do i end up in a 504 gateway error page(not sure if it means anything, but below that it says "nginx/1.0.10").
When i go to check if the message was actually sent(because i used to get a similar error page before this bug started happening, but the messages were sent regardless), it was only sent to a single player, the first one in the player list specifically.
My browser version is: (do not change)
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36

That sounds very odd - as someone who routinely sends messages to groups of people (sometimes as many as 20 players at a time!) I've not experienced this, but I'll keep an eye out going forward

The same thing happened to me, when i tried to send PMs, even to just one person!

I'm using Google Chrome in Windows 7