APEX: Initial value doesn't showed in the calendar as selected day

[pdbocchioKIU]

I have an APEX page item and the initial value is set through an after header page process.

The value is displayed in the input field correctly

but when I open the datepicker none of the days are selected

Is this a bug?
Are there some workaround to "mark" the days selected?

Thank you very much
Regards
Pablo

[pdbocchioKIU]

Another bug I found, once a date has been selected, it is not possible to deselect it.

Can you help me?
Thanks