When using Date/time Picker, OK button does not close the date picker dialogue

Hi folks,

Fairly new to this
I am using a text field for "date of birth" that I added a date/time picker action to it, when running in Test Mode, when Date/Time picker pops up on "changing focus" and a date is picked,OK (or even Cancel) button does not work and the calendar dialogue never closes

Even clicking on a different area never closes the calendar and it keeps showing up

Any help is much appreciated

Thanks,