This can be a few things.
1. Check if you're getting actual data gaps. This could be due to a performance issue.
2. Check if the metric in the metric group isn't getting pushed out. The metric group will show the top N values of the metric regex
3. For the dashboard not populating fast enough, sounds like you have quite a bit of metrics in your smartstor.
Are you seeing this on Workstation (thin or thick client), or Webview or both?
Your best bet is to open an issue and upload the logs directory of the MOM to the issue.