My 2008 Mazda 6 (2.0 petrol/lpg) has been throwing a management light for the catalytic converter about once every 200 miles, although now its starting to get a little more frequent. She also plays up in the rain with inconsistent power levels/stuttering on acceleration. I'm thinking it might be an issue with the precat O2 sensor.

Does this sound likely? Does the freeze frame data show any obvious issues with the O2 sensor?