A VIP drop has been observed during during an Active/Passive upgrade of a two member PPS cluster.
Problem or Goal
Internal testing has shown that during an upgrade of an A/P PPS two member cluster, the VIP is unclaimed near the end of the upgrade procedure for 15-30 seconds.
The cause is that the internal process handling VIP ownership is getting restarted unexpectedly and cleaning out all IP connections including the VIP when it should not be.
This will require a code fix. As of the writing of this bug, it is slated for a Q1 April 2020 timeframe. This fix has not yet been assigned a release version, but I will update this KB as we progress forward.