# History Bug

**URL:** https://discourse.shapr3d.com/t/history-bug/32576
**Category:** Modeling Questions
**Created:** [June 25, 2024, 8:59am UTC](https://discourse.shapr3d.com/t/history-bug/32576 "2024-06-25T08:59:39Z")
**Posts on this page:** 1
**Showing post:** 48

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### Author: ![Istvan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/istvan/32/23668_2.png) [@Istvan](https://discourse.shapr3d.com/u/Istvan)
#### Post date: [June 27, 2024, 9:42pm UTC](https://discourse.shapr3d.com/t/history-bug/32576/48 "2024-06-27T21:42:53Z")

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The issue that can cause this problem is a bug in Siemens Parasolid, the underlying modeling engine of Shapr3D. The problem is that some direct modeling operations can be flaky (providing different outputs for the same inputs). To avoid this situation, we are always going to serialize the entire Parasolid session, and load it when you open the design, to guarantee that there is no feature tree evaluation is happening when you reload a design.

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_[View the full topic](https://discourse.shapr3d.com/t/history-bug/32576)._