Magic Mouse suddenly quit responding on certain surfaces

The Magic Mouse which came with my iMac (27" Late 2013) suddenly stopped working today. It will connect and disconnect normally when you turn it on or off, but the tracking is almost totally unresponsive on a black mouse pad or white piece of paper. On my wood desktop surface it will move some, almost normal but still too erratically to use. Clicks seem to work as normal.

I've changed the batteries, disconnected/reconnected, restarted, deleted the related preference files (per an old community post on the subject), cleaned the optical sensor area with a soft lens cloth and compressed air. No change.

Utterly bizarre. Any ideas, anyone?