Pipelayer crashed while cutting & pasting my sulfuric acid setup. It's copying (but not cutting) the underground layer pipes, even when just copying tiles only, and I think there was too many pipes in one area and it crashed. I reloaded and took a look to find this mess, and using the deconstruction planner caused this 2nd crash: https://imgur.com/a/7bpiGLG, so I had to delete them by hand.

Thanks for the report! The cut tool is not working properly, and I'll work on that. Taking a blueprint on the surface captures both above ground and underground entities. With a normal blueprint you can filter out the underground entities in the blueprint setup window, but there isn't one when using the copy tool. I think I was able to find the source of your crash, and it should be fixed in the next version once I figure out cut.

Could you try the latest version? The cut tool should be properly supported now.