perhaps your system has insufficient RAM for smoothing? Do you have a large segmentation volume? Perhaps try cropping the volume or filtering/downsampling to mitigate computational times…
In my experience that’s almost always related to choosing a smoothing kernel size unrealistically large. Keep in mind the the smoothing kernel is specified in physical units (in mm to be precise), so if you keep it like 3x3x3mm and your voxel size 0.02mm then you will have kernel size of 150x150x150 which will stall and result in out of memory. Make sure the kernel size you specify makes sense in terms of voxel dimensions, you typically want something in the range of 2-5 voxels.