Building completion issue

Summary: I’m trying to build the Carpenters Shop but it refuses to complete. I tried removing the tree to see if it was interfering but to no avail. tried to build ladders to allow access to the roof (which seems to be when it fails). City wall is 3 blocks away from building, and cottage on the right is 1 block away.

Expected Results: Building to complete

Actual Results: Building does not complete


Version Number and Mods in use: No mods, Alpha 18 (3092)

System Information: i5/8gb ram/GTX660/Windows 7

develop-3092 (x64)…hearth/components/scaffolding/scaffolding_region.lua:699: attempt to index a nil valuestack traceback:
[C]: ?
…hearth/components/scaffolding/scaffolding_region.lua:699: in function ‘_start_erasing’
…hearth/components/scaffolding/scaffolding_region.lua:226: in function <…hearth/components/scaffolding/scaffolding_region.lua:219>

develop-3092 (x64)c++ exception: lua runtime errorstack traceback: