HA FTD fails over when deploying VDB updates

[mickyq]

A pair of Firepower 2140s in HA configuration failover when deploying the VDB updates. Failover history shows:

Inspection engine in other unit has failed due to snort failure

my understanding is the deployment will cause inspection interruption but why does it cause the failover. 

[Mark Elsen]

 - Review these bug reports : https://bst.cloudapps.cisco.com/bugsearch?pf=prdNm&kw=Inspection%20engine%20in%20other%20unit%20has%20failed%20due%20to%20snort%20failure&bt=custV&sb=anfr

 M.

[Marvin Rhoads]

This can be caused by defect CSCwf34450.

The bug is present in FTD 7.2.4, fixed in 7.2.4.1 and 7.2.5.