1) Delete (or rename to .off) these 3 files in "C:\Program Files (x86)\Steam\steamapps\workshop\content\108600\3536052310\mods\Neat_Building\42\media\scripts\entities":

• \neat_expand\outdoors\entity_outdoor_smalllogpile1.txt
  
• \outdoors\entity_tarp_shelter.txt
  
• \walls\entity_metal_wallframe.txt

Note: this may prevent the placement/crafting of those objects.

2) Normalize “face single/Single” → “face SINGLE” in Neat Building’s entity scripts (PowerShell, 2 lines):
After this, enable: Neat UI → [B42] Neat Crafting V1.5 → Neat Building → Neat Crafting – Addon XP Display → Neat Building – Addon XP Display. Loads fine on my setup.
Note: Workshop updates may overwrite these changes; re-apply if needed.

No PowerShell? Edit these files manually and replace “face single" or "face Single” with “face SINGLE”:
agricultural\workstations\entity_cooking_pit.txt
agricultural\workstations\entity_simple_cooking_pit.txt
blacksmith\workstations\entity_charcoal_burner.txt
blacksmith\workstations\entity_charcoal_pit.txt
blacksmith\workstations\entity_furnace_iii.txt
furniture\entity_other_log_stool.txt
neat_expand\fences\entity_fences_logcorner.txt
neat_expand\floors\entity_welding_meshfloor.txt
neat_expand\furniture\entity_furniture_smallwoodencase.txt
neat_expand\furniture\entity_welding_shopclothingstandrack.txt
neat_expand\furniture\entity_wood_fancycornerbookcase.txt
neat_expand\outdoors\entity_welding_ironbandbarzier.txt
outdoors\entity_chopping_block.txt
outdoors\entity_tree_stump.txt
walls\entity_woodenpole.txt

Rocco (author of Neat Building) is aware of the 42.12.0 breakage; an official fix may take some time.