Alerting stuck at white heart status for new Dashboards ?!?

Looking for some pointers. I am creating new alerting dashboards via the API, with alert configuration enabled for a number of graph panels.

What I see is that the Alert status never moves from Pending to Alert for some reason.

Even though the Test Alert shows it as ‘firing’ it never transitions from the white heart status.

When I save the dashboard via the UI, this then resolves the problem and the Heart status moves from White to Orange then to Green or Red as appropriate.

Grafana version is v6.5.1

Looks like will be related this issue