Contact form throwing 422 response codes

I have just checked using Firefox 146.0.1 logged in and I get the captcha. Brave 1.86.148 not logged in and I get the captcha. Both on Debian Linux 13

I tried on Android Brave logged in and got a captcha.

Also see this: Contact to MT via contact form?

And against better judgement, I tried Brave in a Win 10 VM and also get a captcha.