K3II - raw not being recorded

I was out yesterday with my K3II, which is set to record RAW + JPG, but when reviewing my shots later I realised that the first 15 or so shots where recorded as JPG only.

I'm assuming I did something, but no idea what. Later shots were recorded RAW + JPG. The camera was switched off whenever I changed lenses, so presumably this would have reset it back to my RAW + JPG setting at some point.

Any ideas please?

I've had it happen when a button has been caught while carrying the camera. It's been set to some mode or other I did not want, then you change some setting and it goes away without you knowing it's been there.