If I enable deadline markers and task resizing both at the same time, the deadline markers are preventing resizing if they fall at the very right edge of the task.
I have patched this by adding the following to my stylesheet, but it would be good if this were fixed within the product itself:
/* Ignore pointer events for the deadline markers to prevent these interfering with resizing tasks */
.smart-gantt-chart .smart-gantt-chart-task-deadline
{
pointer-events: none;
}