Seems to be bit old but I am encountering new error. Its error (504) via master 1 , forum is overloaded . However this happened to me two times only. Willing to know if this has happend with any other community people.
I believe you are referring to this forum software (SMF)? I haven't faced any issues on the new beta myself but I'm getting that 504 error here while trying to post or sending private messages sometimes, refreshing the page seem to do the trick. It's worth reporting If you get more errors in the future.
The old error is completely resolved now.
Your "new error" is one I get on this forum and I believe it's due to sending two requests to the server in a second (the server sends the 504 error in order to stabilise itself as it is designed not to do more than one thing to each ip in the same second because it isn't really useful for a forum to neeed to be faster.