It is good that you鈥檙e stress testing the app 
Thanks for the report!
I鈥檓 suspecting an issue with vertical panos could be affecting your results, I have already submitted a patch for it (Feature auto wave correction by krupkat 路 Pull Request #67 路 krupkat/xpano 路 GitHub) and published a new release (though it is not up on Microsoft store yet). Before the patch the vertical panos had their projection unnaturally stretched wide and this could eat up all memory + cpu.
Since you鈥檙e on Windows, there is working OpenCL acceleration, possibly I can look into enabling CUDA as well, could be interesting.
The new release: Release 0.11.0 - Automatic wave correction 路 krupkat/xpano 路 GitHub