It's simple to reproduce. You need 2 div's. One is needed for Daypilot scheduler (where it's build the calender) and the other is used as parent (the scheduler container is insert in there).
If you give the parent div (with the scheduler div inserted) a margin-top, the tooltip for events will be displayed in the wrong position.
Here example:
<html>
<head>
... load jquery, daypilot js files ...
</head>
<body>
<div style='margin-top:30'>
<div id='dp'></div>
</div>
<script type='text/javascript'>
var dp = new DayPilot.Scheduler("dp",options);
</script>
</body>