Captcha on Unity Answers shows error message

There's a "prove you're human" captcha if you want to post on Unity Answers.
Solving it is really slow and it often also refuses to verify me (which is a known but ignored problem on the Google forums) but 4 out of 5 times it additionaly shows an error message, which makes posting tedious:

"The characters you typed did not match the image"

I know what these "character" captchas look like but what makes it weird is that it never shows anything like that, I only get the "pick the right images" ones after clicking the button, nothing else.

I'm using Firefox 61.0.1 without NoScript, so it's not like that could have blocked it.

Is Unity Answers maybe still using an old version of the captcha, which makes it show this old error message? Can anyone please look into this?

 

Bump. Still an issue.

 

Don't bother using Unity Answers. Nobody has bothered to maintain it in ages and there's only one or two active moderators anymore.