Unusual root motion native crash in release build

We have one user who is experiencing native crashes consistently which we were able to locate in Unity Crash Reporting. They are so unusual I was hoping someone else had come across them before and could maybe shed some light on them.

Multiple occurrences of:

Native Crash - ?EvaluateRootMotion@animation@mecanim@@YAXAEBUClipMuscleConstant@12@AEBUClipMuscleInput@12@PEBM2PEBUGenericRootXReference@12@AEAUMotionOutput@12@AEAUMotionXReference@12@_N66@Z (c:\buildslave\unity\build\modules\animation\mecanim\animation\clipmuscle.cpp:1184)

1 occurrence of:

Native Crash - ?rasterizePortal@RasterOps@Umbra@@SA_NAEAVBlockRasterBuffer@2@AEBVVector4i@2@AEBUVQuad@2@AEBUAxisNormals@2@AEBV32@@Z (c:\buildslave\unity\build\external\umbra\source\runtime\umbraportalraster.cpp:1441)

Only this 1 user across our substantial userbase has ever had these crashes. Nothing particularly unusual about his spec really. Ryzen 5600X running at stock speeds, RTX 3060 also running at stock speeds, 16GB RAM. As soon as a AI agent is instantiated in the game that uses a root motion based animator controller it crashes.

The release build was created with Unity 2019.4.30f1 and uses il2cpp as the scripting backend