Challenge
By default the alarm has the following settings on Rules tab:
VmDisconnectedEvent and VmConnectedEvent are sent out by Vcenter Server in case the host where a VM resides by any reason was disconnected from Vcenter or any other issue.
In the alarm history a state change during a certain period of time can be observed
Detailed investigation and analysis of the database of Veeam Monitor shows that there are 2 events to be received from a vCenter server:
As displayed on the screenshot, there are 2 events in last alarm state record. This mean that 2 events has been received simultaneously and have equal time stams.
Cause
Most likely a host experienced a connection state change within 1 second (a network link blinked or anything else). Further on a host could be working stable but the host connection state change generated 2 events: disconnection and connection. Both events came at the same time to Monitor Server, but Monitor considered that a VmDisconnectedEvent has been received later than VmConnectedEvent thus showing the "Error" status as the last alarm state.
Solution
Resolve the alarm though Monitor GUI manually: