Thanks both!

The reason I initially thought the problem might be my setup, and not the album, was that I had had similar problems previously with a (non-folk) album. That album was quite loud and grungy; the impression I got was that the additional vibration from the loudness of the guitars was making the sound distort, and in a couple of places kicking the needle right out of the groove and making it skip. (I don't know if either of these things can actually happen.)

Anyway, I didn't think any more of it until I played the Carthy album, and had similar problems on much quieter tracks. I'm wondering now whether the problem is with my stylus - although unfortunately I don't have a microscope to hand!

Now thinking of buying a weight gauge and doing the tone-arm weight thing properly - and a new stylus to be on the safe side.