I’ve been trying to build the double house several times now, but it errors out each time. I’ve found at least 3 different ladders stuck inside blocks and that seems to cause the building to stop and stay incomplete. I think there is a fourth one that I don’t see, since there is usually a very small one left hanging quite far up in the air after I remove the partial building.
I’ve been using the main template without changing it. Version a20r699.
Also, if I do remove the stuck scaffolding/ladders, is there any way to get the workers to complete the rest of the building? The last try ended up finished except for the doors, a couple of windows, and the oil lamp (after I spent a long time removing the horde of ladders and pieces). 
Edited to add: The true name of the template is Red Clay Homes.