Yeah it’s really strange but I’ve had this problem on other sites too, had to put in several different measures (recaptcha, honeypot AND stopforumspam list checkers) before it stopped.
No JS errors relating to the form at all, and trying to register without ticking the Captcha doesn’t work either.
Looking at my Captcha console it definitely is blocking *some* of them but I’m still getting so many registrations that are clearly spam judging from username & emails.