it is caused by editting a building that is currently being built and having them build onto it with edits.
error:
develop-2620 (x64)Unknown C++ exceptionstack traceback:
[C]: ?
[C]: in function ‘add_unique_cube’
…arth/components/fabricator/fabricator_component.luac:333: in function <…arth/components/fabricator/fabricator_component.luac:314>
[C]: in function ‘modify’
…arth/components/fabricator/fabricator_component.luac:314: in function ‘_update_fabricator_region’
…arth/components/fabricator/fabricator_component.luac:364: in function <…arth/components/fabricator/fabricator_component.luac:364>