## Bug description

When going to instance status > internal metrics and refreshing the dashboard, the loading fails

https://user-images.githubusercontent.com/148820/120655500-693c7480-c48b-11eb-8c75-6afd4c967506.mp4

## Expected behavior

It reloads successfully

## How to reproduce

See above

## Environment

- [x] PostHog Cloud
- [x] self-hosted PostHog, version/commit: latest

## Additional context

Seems the cause is that "refresh" requests data from `/api/insight/trends` vs getting it from `/api/dashboard/id` as on first load.

Relates to #3609  

#### *Thank you* for your bug report – we love squashing them!

posthog/api/dashboard.py
if self.get_result(dashboard_item):
            return dashboard_item.last_refresh
        dashboard_item.last_refresh = None
        dashboard_item.save()
        return None
    def to_representation(self, instance):
        representation = super().to_representation(instance)
        representation["filters"] = instance.dashboard_filters(dashboard=self.context.get("dashboard"))
        return representation
class DashboardItemsViewSet(StructuredViewSetMixin, viewsets.ModelViewSet):
    legacy_team_compatibility = True  
    queryset = DashboardItem.objects.all()
    serializer_class = DashboardItemSerializer
    permission_classes = [IsAuthenticated, ProjectMembershipNecessaryPermissions]
    def get_queryset(self) -> QuerySet:
        queryset = super().get_queryset()
        if self.action == "list":
            queryset = queryset.filter(deleted=False)
            queryset = self._filter_request(self.request, queryset)
        order = self.request.GET.get("order", None)
        if order:
            queryset = queryset.order_by(order)
        else:
            queryset = queryset.order_by("order")
        return queryset
    def _filter_request(self, request: Request, queryset: QuerySet) -> QuerySet: