Unfortunately I don't know what caused this issue or have any ideas on a workaround. However, the developers at Devetry have been working on FloorspaceJS for several clients and have fixed a number of bugs. I have seen some work on this issue but it has not been closed yet. You could browse the open issuesand make comments or upload test files to help diagnose and fix them. You might also be able to try using the latest version of FloorspaceJS in your browser at https://nrel.github.io/floorspace.js/ to see if the issue is still there. I am planning to update the version of FloorspaceJS inside of OpenStudio for the 2.9.0 release.