With a dialog template on a kanban object, if you do do args.cancel=true onDialogOpen, it leaves the following artifact behind thus breaking the next dialog window attempted to open.
<div class="e-dlg-container e-dlg-center-center" style="z-index: 10000007;">.....
Adding this after args.cancel=true, resolves the issue as a workaround:
$('.e-dlg-container.e-dlg-center-center').remove();