Hi @Anonymous,
Does your AutoCAD have any plugins or customization? If you create a brand new (administrator) user on your computer and then launch AutoCAD does the behavior continue? Is it possible to attach a sample file with the pline that disappears once exploded?
More importantly, please update your AutoCAD today to the latest version. (.02). If you don't do this today your AutoCAD will fail to run tomorrow. For more information, please see this post.
Please select the Accept as Solution button if my post solves your issue or answers your question.
John Vellek
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