There are few rules to follow when you edit a family.
1) Use consistent values when changing parameters.
2) When editing a closed profile you always need to obtain a closed profile;
3) Right now it is only possible to add lines and arcs to modify profiles. Please check that all new entities belong to the right categories.
4) If you delete a category of entities, the connected 3D elements are not created. This may be useful to create customized spiral staircase.