Let me answer you from my own experience
I had a little less than a dozen devices that became 'down' in NPM all of a sudden.
I am able to login into the devices, they all show to be up, working, healthy, etc.
I went back to the NPM and started to look at the devices configuration, checked it, nothing had changed but NPM could not see the devices.
After looking more closely at what devices were down, I found that they were all on the same network, that network was in a DMZ. i checked the FW rules and notice that someone had removed the rules to allow SNMP traffic to that network.
So the devices were not down, NPM could not reach them.
So my hypothesis is that a link between your Solawinds server and your device came down for 5 minutes which make NPM think the device was down when in actuallity, it wasn't.
Hope this helps.