This is not always reproducible but happens often to be of a small concern.
The scenario is as follows:
Have a group of platforms down with a down alert fired for each of them.
All the platforms come up within a short interval (under 10 minutes) causing recovery alerts to fire for each of them.
For one or two platforms the platform availability down alert fires immediately after first recovery alert fires and within 1 minute recovery alert fires again (1 minute is platform's availability metric collection interval).
The duplicate down and recovery alerts are not expected.
I did see a spike in availability inserter queue size in hq-stats and the spike lasted less then 30 seconds. The spike may be a symptom of availability inserter slowing down causing backfiller to fire down alert.
See attached screenshot, in this case the platform resource was brought down at 1:01 PM (along with many other platforms) and was bought back up ~2:10 PM> This caused 2 down and 2 up alerts to fire instead of just one of each.