Scheduler - Cannot read properties of undefined (reading 'ignoreDisabledCells')

I'm getting the following error, when I add events to a top frozen row. If the row is frozen to the bottom, the error doesn't occure.

TypeError: Cannot read properties of undefined (reading 'ignoreDisabledCells')
    at DayPilot.Scheduler.Ts (daypilot-pro-angular.mjs:9663:28)
    at HTMLDivElement.Gr [as __zone_symbol__ON_PROPERTYmouseup] (daypilot-pro-angular.mjs:9654:42)
    at HTMLDivElement.wrapFn (zone.js:763:39)
    at ZoneDelegate.invokeTask (zone.js:406:31)
    at Object.onInvokeTask (core.mjs:26505:33)
    at ZoneDelegate.invokeTask (zone.js:405:60)
    at Zone.runTask (zone.js:178:47)
    at ZoneTask.invokeTask [as invoke] (zone.js:487:34)
    at invokeTask (zone.js:1600:14)
    at HTMLDivElement.globalZoneAwareCallback (zone.js:1626:17)

This is the code that adds the events:

private createPlanningCommentEvent(item: PlanningComment) {
    return <AttendancePlanningEvent>
      {
        id: DayPilot.guid(),
        text: '',
        resource: this.getPlanningCommentsResource().id,
        start: new Date(item.date).date().addHours(12),
        end: new Date(item.date).date().addDays(1),
        backColor: 'transparent',
        borderColor: 'transparent',
        resizeDisabled: true,
        moveDisabled: true,
        toolTip: `<b>${this.dialogTextService.getTranslation('TitPlanComment')}</b><br>${item.comment}`,
        areas: [
          {
            css: "scheduler_centered-time-header-icon",
            image: 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAACxIAAAsSAdLdfvwAAAAHdElNRQfhDAgPAhOsXMMIAAAAGXRFWHRTb2Z0d2FyZQBwYWludC5uZXQgNC4wLjE51NayZAAAAKdJREFUOE+1k8ENwyAMRd3NOkKHgVulzFAJdQJfERy450I3YB9qt0YqkZWEtP3SUwjx+3AJ/CQxxosxBolpJ8iO6AC8QdRBUPRXAbdqQ2tMovcFW2lz7IjeF6SUqnNOhb+1OXZE//MN+L1RStku0LK4ekMv4FM+T805V0RcyoxesBdr7V308QKSq/f+KnpXcJOtsYQQZpIftDy9dwZDP8aZHsfk7wLwBLS2mmj33LmDAAAAAElFTkSuQmCC'
          }
        ],
        tags: {
          type: 'PlanningComment',
          data: item
        }
      };
  }

getPlanningCommentsResource() {
    let resource = this.personResources.find(r => r.frozen !== undefined);

    if (!resource) {
      resource = {
        id: DayPilot.guid(),
        name: '',
        frozen: 'top'
      };

      this.personResources.push(resource);
    }

    return resource;
  }