I have created an host accessibility (using port and URL-based uptime checks) dashboard to display outages and have run into an issue where 2+ minute outages are being reported as separate 1-minute outages. In other words, a 15-minute outage is displayed as 15 one-minute outages. This problem has some time in the past two months and no configuration changes were made which leads me to believe it could potentially be an issue with Dynatrace 6.5 because I didn't have this occur with 6.3.
Below is an image of a generated report for the TCP port and URL-based checks illustrating the issue:
If you think this has changed since the upgrade then please open a ticket. The support team can tell you whether there are any known issues -> maybe already a new update that addresses this.