Blank image on subscription email

[prihana]

I have about a dozen dashboards set up for my organization. Most of them have an email subscription with daily updates. 
From recent, a randomly one of the image of any of the dashboards comes as an empty snapshot. It doesnt happen to the same dashboard again and again, its a different dashboard everytime.
When I resend the same dashboard it doesnt happen again. What could be the issue?

[lbendlin]

could be a server overload that results in rendering timeouts.  Work to make your subscription page render faster and also talk to the capacity admin to see if they can paint some "go faster"  stripes on it.