A family of gremlins seems to have taken up residence in our TV setup. Sometime yesterday afternoon, our TV suddenly and magickally start turning up its own volume.

Over a space of a few seconds, the volume will go from 0 (mute) to 100 (max. volume, nominally +15.5dB). You can [try to] turn it down, but your swimming upstream -- the gremlins are turning it up as fast as you can turn it down. The mute button is good for about a half-second.

Since the TV is connected to our A/V receiver via HDMI ARC and the receiver and TV both support HDMI control, this drives, in parallel, the amp's volume to its max. And since the amp is 5x90 watts continuous + a 105 watt subwoofer amp, it's bad.

Figured maybe it's something to do with the HDMI control stuff, but no. Disconnected the TV completely from the amp, and it still exhibits the same problem.

Some googling shows that this seems to be a known problem with Sony Bravia TVs. But not, seemingly, to Sony.

Following some of the steps to resolve the issue, it's still a problem.

Some of the "solutions" posit a stuck volume button on the remote (not an issue, I can turn the volume up and down, as long as it's before the gremlin takes over, and the problem continues if I've removed the batteries from the remote). Others even involve opening the back of the TV and removing/disconnecting a circuit board -- not sure I'm going there.

We even did a factory reset of the TV to no avail.

I'm stumped.

Any ideas, before I call Sony?