BlueCat Server Update Services has the following known issues:
Multi-stage updates on xHA pairs might lead to unexpected behaviour
When applying multi-stage updates to DNS/DHCP Servers operating as an xHA pair, certain role transition scenarios might lead to unexpected behavior during the update sequence, such as additional processing of update steps on the primary node. This behavior is limited to multi-stage update operations.
Due to xHA role transition timing considerations, for Server Batches that include xHA pairs, BlueCat recommends applying upgrades and patches sequentially rather than in a combined multi-package.