Hi Normis,
since 2 days the Forum respond with ERROR 500 on any reply post. The post is actually done , but the screen says it failed.
I also see many double posts from other users. It is very tempting to just re-post the same still open post.
You don’t accept private messages, so sorry to use this public path.
Have you tried other browsers, maybe Private mode with no plugins enabled?
When making the first reply, I also had the same problem. Our administrators are now checking the problem 
Yes. Mobile Chrome returns the error, Firefox without any adblocks just shows a blank page, and notification e-mails stopped coming at about the same time. I hazily remember last time this was happening, it took ages after posting to get the page reloaded, and it was said it was linked to SMTP issues. Maybe the current behaviour is a fixed version of that one (instead of waiting for the e-mail sending thread, an error is reported straight away)?
OK Thanks. Trying this with another browser. I did not change anything to my browsers but Google and Microsoft update continously in the background.
EDIT: Edge just gave me a blanc page when posting.
EDIT2: editing works fine (now?).
Looks like it’s fixed now
NOPE.
Happens since about 2 days also in my Opera web browser in Linux.
It says
This page isn’t working
forum.mikrotik.com is currently unable to handle this request.
But the posting still goes thru.
Ie. the above error message happens when making a posting. But the posting still gets posted successfully.
Another problem is: email notifications no longer come in. I wrote about it also here: http://forum.mikrotik.com/t/mikrotik-notification-server-down/140357/1
Can you try the same from another browser in private mode?
Ok, making this reply in an other browser (Firefox Linux) in a New Private Window…
The result was: BLANK WINDOW with no text at all in the window. But the posting went through.
But: the error did not happen when EDITING+POSTING the post… Hmm…
True, confirm
Problem is still there. Quite disturbing, reloading the page or going back to the prevous page is likely to post the same content again.
I am now well trained expecting the problem and working around it…
The forum is probably running ForumOS 6.47 STABLE 
i have also sometimes a odd error when i open the forum. Reopening the forum solves the problem.
any clue ?? pls help
now works for me.
Received a notification for this post. So they fixed it.
Thanks MKT,Normis.