what's your pulp recipe and what's the consistancy (is it relly moist or kind of dry)?

roughness can be corrected with sanding and some sort of varnish.

i'm not sure, but it may have something to do with the drying time. a lot can happen in regards to shape and consistancy while drying, especially if it takes a long tme to dry and there's a lot of pulp to dry. i also don't know how you apply your pulp, but be sure to do it in layers , allowing different sections to dry completly before continuing. it will assure a complete dry sculpture with little wet to dry warping. i'm not sure what you mean by "carving" in that either you carve away the dry mache or you make patterns in the wet pulp. if it is the latter, you may want to wait until after the pulp is dry, or nearly dry before making patterns in the pulp. since your pulp is fairly moist and mushy,  etched in patterns probably wont remain consistant through the drying time.

good luck.

if you apply too much to fast, the drying gets weird. the inner layers will dry much slower or not at all, which could mess with the integrity of your sculpture.