I’ve had a web chat with Avast support, so I know the current answer to this, I’m just sharing.
In the portal, several devices are showing their status as ‘In danger’ and when you look, they report the shields are disabled by user. Yet when you look on the machine, the shields are indeed on and working fine. Seems to be OS X clients, but randomly so.
Support said ‘it’s a known bug’ but can’t give me a reference, tracking number or an estimate to when the developers might get to look at fixing the issue.