This may not be the answer to the original question, but the false-positive alerts on my end are the result of a bug in vCenter 6.0 where received packets are reported as dropped, even when they actually are not. I opened a Support case about it and was referred to the following KB (2052917). The issue has been fixed in 5.1 and 5.5, but not 6.0.
The workaround is to disable the metric for received packets dropped. In my experience, when I attempted to disable the alert or symptom in my policies, the presence of the enabled metric still caused the alert to be reported. That feels like a bug, too, but the root issue is with the metric, so I'll accept that necessity for now.
Thanks,
Chris
