I’m not sure what could cause this, but if you could open the form, hit F12 to bring up the console and then type in this (replace DateColumn with your fields internal name):
var dfo = spjs.dffs.getRegionalSettings().DateFormat;
var sDate = spjs.dffs.strToDateObj("DateColumn", dfo);
sDate
Does the sDate value show the same as the datepicker in the form?
Alexander