[Elecraft] "Turn on the KPA500" Error

[Stewart Bryant]

I have a K3 connected to an XV144 in the preferred configuration shown 
in the manual with the AUX port used for band switching.

Occasionally I find that with the XV144 powered down the K3 hangs 
complaining that the KPA500 needs to be turned on. I can cure this by 
powering on the XV144 or by disconnecting the Aux lead from the XV144.

Is this a fault on one of my component's (K3, cable or XV144), a bug or 
a feature.

Any idea where I should start to debug?

Thanks

Stewart/G3YSX