I cannot post complex posts either. Exactly the same error shown in your screenshot.
I am posting from Germany,in case it matters
I have same issue regarding posting more than a few lines
This also affects private messages.
Another issue is the disappearing of text when you edit a post.
Very very annoying and frustrating.
Lost a few good posts and wasted hours. :rolleyes:
Used Safari on Mac and also tried Edge on Windows 10 -> specifically for the editing issue
Sorry! Didn't mean to offend! Of course you can do whatever you like in your own thread ;)