I am having the same issue. The page in question for us is https://www.oakdalefusion.com/camper-registration
Specifically in the Camper Information form, the fields for 'Grade Completed' and 'T-shirt Size' are both dropdowns that are leaving an extra option.
Inspecting the element doesn't show an extra option, but it does have an 'optgroup' at the bottom with a blank label.