Undefined date on DragEnd


Sometimes I get an unqualifed date when I drag an event:

scheduler.attachEvent("onDragEnd", function(id,mode,e){
var task = scheduler.getEvent(id);
var zkp = task.id;
var description = task.text;
var formatFunc = scheduler.date.date_to_str("%d-%m-%Y");
var date = formatFunc(task.start_date);
var dend = formatFunc(scheduler.getState().min_date);
var List= [zkp,description,date,dend];
    return true;


var date return empty time to time, I don’t know why,
If someone have an idea, thanks in advance <


It is not a known issue for us. I tried to reproduce the issue in the snippet tool, but unseccesfully.

Please try to do it in the snippet and if you can specify what should I do to return unqualified date or at least send video - it would help me to understand.