Some users experienced missing data when the email was sent. Random fields were not included in the email. After much research, I concluded this must be due to the size limitation of a cookie. Browsers generally limit the size of a cookie to 4,093 bytes which is roughly 4,000 english characters, which is roughly one typed page double-spaced. So it’s kind of a lot. However, some websites do require large multi-step forms. For those websites I’d recommend going with a different plugin called Formidable Pro. It has helped me tremendously doing an online application.
If you still would like to use Contact Form 7 Multi-Step Forms, lucky you, there’s now a Pro version available. Contact Form 7 Multi-Step Forms Pro uses Session Storage which can hold 5 MB of data. That’s about 1,000 times more than a cookie (or 1,000 pages double-spaced)! It works the same way as the free version except that it will work on large forms.