What can cause a CARP interface to remain "master"?

[MrPete]

I've got failover mostly working.

One anomaly: with half a dozen VLAN interfaces, plus WAN, if I failover: one VLAN and the WAN don't failover, unless/until I force it by going into maintenance mode.

I see nothing special, particularly about the anomalous VLAN. Have looked at skew, every other config I could think of.

Ideas?

[MrPete]

@mrpete FWIW,
This effect has simply disappeared over time.

I have no idea what the root cause was.

I can't say failover is 100% reliable yet, but it "mostly works" and that's good enough for now. I need to move on to more urgent issues.