Panasonic FZ150 Raw conversion

I have a panasonic FZ150 which creates RW2 raw files. About 5-7% of the raw photos are not readable on import, but they work fine with other programs (Autopano, Adobe) and appear to be fine otherwise. Any ideas why they do not convert in Aperture?

I have verified the disk/disk permissions, rebuilt the library, and checked to see that my firmware was up to date. These came from several chips, so it is not likely that the chip in the camera was a problem