Sometimes and seemingly randomly I will get the following error message pop-up after posting a reply to a thread:

This has happened on both desktop Firefox and mobile Orion. It's seemingly random but today I've got it twice in a row. Posts seem to go through just fine, I haven't noticed any "real" issue with anything besides the presence of the pop-up itself. I have also not noticed it when creating a new thread, seemingly only when replying. Could be mistaken on that part however. I did not get the message when posting this thread.
Would expect for there not to be a pop-up when posting.