Date Validation

Hello all 🙂
I have been using the form builder for a couple of weeks and thought all was well.
However, I have had some folks contact me as the form will not accept the date they entered — so I tried it myself. I tried it with the date of 11/05/1998 and it worked — tried again with 03/28/2007 and got a date error (“incorrect value”).
So, I thought I’d just remove the validation… however, when I edit the field and click to save the change, I get bounced to a 404 page not found…
http://wildflower.sd8.bc.ca/about-wildflower/interested/ is where the form is running…
Help!

https://ww.wp.xz.cn/plugins/contact-form-builder/