Hi Dan,
The following command seems to have no effect (or at least does not trigger DayPilot.Scheduler.onBeforeCellRender:
DayPilot.cells.all().invalidate();
DayPilot.cells.all() does contain all cells, but the invalidation does not take effect.
DayPilot.Scheduler.update() does work however and trigger the onBeforeCellRender correctly.