Umbra occlusion culling stopping after 'Computing Occlusion'

Computing the occlusion data here seems to never end and stops at 'computing occlusion' with the blue bar to 100%. If I click cancel unity will just freeze, same when I tried to change scene. I have managed to bake the data in other projects and seems to only have started happening since the update to the new method of Occlusion Culling. Is it still working and just taking forever to compute, or is there something going wrong?