Hi there,
I have been using Formidable with Stripe for event registration on a website, and we have been getting an occasional "Invalid email address" error when people are trying to sign up with valid email addresses. The issue is reportedly happening when they click submit. 
When searching the forum and Googling this issue, I have not found any other mention of it. As it is really intermittent, I have not been able to replicate this issue myself. I also tried using the email addresses that were used when the first error appeared to do a test submission, and I did not get any errors at that time. 
I am wondering if anyone has dealt with similar issues and if so, what was the solution.
Thanks!