I cannot reproduce your situation, is it still happening because i see you have managed to edit articles since posting here? , it seems it might be a local issue? Have you tried pressing the attempt a fix button on the error message?

It comes and goes. Sometimes I can work for a while without getting it, other times it pops up every few minutes.

I'm in the same boat. I use Firefox on Windows 11. The computer is an Asus TUF Gaming A17. I have also tried hard-refreshing. The box pops up randomly, sometimes not showing for hours, and then re-pops up. I even tried clicking on "click here" to fix it and it would pop up again within a few minutes. Usually it would be after I finished adding in a container box for my articles. I took a picture of the issue and added it to this post (I hope it shows up).  

Update about the container-boxes....it seems to be with the [ symbol rather an entire BBcode, as it just happened when I was trying to add a dice button to my D&D session notes.

i have been having this issue as well. the guild feature button has been disrupting my work, but i will try the suggested methods.

I will be closing this since we cannot reliably replicate it