discovered ReCaptcha issue. Assumption in the code is that ReCaptcha wouldn't appear until the user tried to submit the form, and that was always my experience, but it turns out it's possible to get a ReCaptcha response early, at that point the form gets submitted whether it's filled out or not.
refactored
this helped: https://stackoverflow.com/questions/49364689/captcha-form-validation-required-error-message-in-vue-recaptcha