custom fields values disappear when the form is not correctly filled

-- HikaShop version -- : 3.1.1
-- Joomla version -- : 3.7.4
-- PHP version -- : 7.0
-- Browser(s) name and version -- : chrome 60

I created a few "order" custom fields which the user fills up before sending the order, like custom date of delivery. Some of them are required. Now, if a user submits the form without all the required values filled, all the inputs go blank! The expected behaviour should be - remain all the values he/she introduced.

Is it possible to fix?