I shoot raw + JPG on a 1D IV, sending the raws to the (bigger, faster) CF card and the JPGs to the SD card. I've done this for many years.

But since a week or two ago, when I delete a shot in-camera, it only deletes the raw file, leaving the JPG behind. It's never done this before. I haven't changed any relevant camera settings that I'm aware of.

Before I go nuts trying to figure it out, has anybody met this odd-ball behaviour before?