It went away for a while weeks back but recently it has gotten worse again. It comes and goes both randomly and in severity. Sometimes the delays are just a few seconds, other times, they can last for minutes.
One minute, all is fine, the next minute, the site freezes. Earlier, while waiting for a message to post, I tried opening my Alerts menu for something else to do while waiting, and instead of the two requests being serially stacked in the que, the second request cancelled out the first and I had to go back and make a second request to post the message.
I finally realized that most times when this happens, if you watch in the upper right corner (to the right of SEARCH), you'll see green bars flashing indicating Xenforo operating in the background much like either it or the server is clogged with too many requests all at once.
The idea was proffered about changing the site to a pay site with an annual fee. I'm good with that.
This same matter was addressed maybe a couple months ago by one of the Admins, and I think his conclusion was something about too many bots and stuff clogging up the pipeline. After that, someone deleted a ton of bots and the problem seemed to slowly clear.
So instead of seeing 150 members and 5000 "guests", the guests were brought down to more like 1500.