When opening a project in Fuse 1.2.0 (build 13961) it was stuck with the text “building project…”. No error message in the log or problems area (which i also think is a bit confusing, with two places for error messages.). I Then tried to build the unoproj file from command line and sure it threw an error, it wasn’t able to parse the unofile. I was missing a comma in one of my arrays.
I think the preview tools should return some indication of failure instead of just being stuck on building.