<input type="date" /> in the form, that may be the issue.
It appears that Webkit has implemented validation for a
type="date" field without implementing matching UI for a date picker or error message to enforce the required date format.
Since the “I need this project done by” field on our project inquiry form does not need to be a valid date format (a response of “by Sept. 1” or “in 3 weeks” is valid in our usage), the choice to use an
input type="date" field was probably a poor choice in the first place. 20/20 hindsight.
Hopefully this will help others avoid losing too much time investigating this issue.