I downgraded to 1.2x firmware. It fixed my issues that sound somewhat similar to this. With 1.3x, literally after a while, the device just disappears for a few seconds at a time, and it comes back. A reboot clears it up for another few hours/days.
I can't officially recommend it, but if you're okay with a certain amount of risk, it might be worth a shot.
I'm trying it now, and so far so good...