Subwoofer cutting in and out

I have a Wharfedale sub that occasionally cuts out. It doesn't go completely off, just very faint. Any movement of the "auto-on" switch, or turning the main power switch off and on seems to fix it for a while. Does this sound like a fault in the auto-on detection?
I've already returned it under warranty, but of course they couldn't replicate the fault and sent it back as "tested ok".
I have no reason to think the amp (dedicated SW out) or cable is at fault due to the volume returning as soon as either of the power switches are touched.
Any thoughts?
Call the guy selling the telephone transponder tweak here on the gon. Maybe he's got a, shall we say, "message" that can be said over the phone to fix it. I was thinking of "cut it out" myself. You can try that yourself and if it works, you'd be done. (Seriously, good luck).
i had a similar problem and i dialed back the level and boosted the subwoofer ouput and it became much more consistent and punchy