I see that happening for 2 users only since 1st of July. This could be an UI issue. Did the users tried to enter the SMS token received, even if the error showed up? In case this happens again and the user is unable to finish the reset password process, please open a support case with us and we can investigate further.
Have you sent a pwd reset link? It could be that the user disnt fullfill the first time after which the token expires in the reset link. If they try the link again it fails, you'll have to send in another link and have the user do the reset in 1 flow