First off, you may not need to export your segmentations to do those calculations. Have you checked Segment Statistics Module which provides some of those Segment statistics — 3D Slicer documentation
And perhaps other metrics you need can be added (or already available) in elsewhere. My first suggestion would be to explore those before you try to use yet another program. Also I think @jmhuie might have already one this as a module. See this post. Calculating Second Moment of Area from Segment - #4 by jmhuie
As for your error, it is not clear to me what’s going on without seeing your data. We routinely export labelmaps from segmentations, and haven’t encountered this error with any of the 4.11 or 4.13 versions of Slicer. if you can upload the segmentation and the volume that give you the error we can try to troubleshoot.