active_members changed behaviour

I have an iRule that generates a status page based on the availability of members within a pool.

It does a "members -list" and an "active_members -list" the output of which is displayed in the status page.

Since we upgraded from 11.3.0 Hotfix 8 to 11.5.1 Hotfix 8 the behavior has changed on one specific pool which has priority groups.

The pool has one server with priority group 1 and one with priority group 2.

In both cases the GUI shows 2 menbers in the pool as active, however since the upgrade the "active_members -list" in the iRule is only showing one server, the one with the higher priority group.

Has anyone else noticed this behaviour and is this a known bug?