Registration form sometimes decides not to work

I’m having some sort of issue with the sign-up workflow, this is the second time its happened that there’s been a block of users who signed up but where I have none of their details recorded. I have no clue what could be causing this.

Second, is a backend workflow that I have set up to send a follow-up email on form submission isn’t sending 1 email, instead it sends like 7 of the same emails all at once. Any ideas what could be behind these problems?

Thanks!