How to reproduce:
1. Open the “CrashRepro“ project
2. Open the Animator Window (Window>Animation>Animator)
3. Select the “Assets/QuantumUser/Resources/Prototypes/Characters/Surgeon/Animations/SurgeonAnimator.controller“ Animator Controller
4. Delete the animation transition from “metarig_KnockbackFall“ to “metarig_Fall“
5. Delete the animation transition from “metarig_KnockbackHard“ to “metarig_Fall“
6. Delete the animation transition from “metarig_Knockback“ to “metarig_Fall“

Reproducible with: 6000.0.36f1,  6000.1.0b4, 6000.2.0a1
Couldn’t test with: 2022.3.57f1 (Errors in the Console)

Reproducible on: macOS 15.2 Sequoai (Intel), Windows 11 (reported by user)
Not reproducible on: No other environment tested

Note: The crash can occur on steps 4 or 5

First few lines of stack trace:
0x00007FFC6BB2837A (KERNELBASE) RaiseException
0x00007FFB67702D92 (Unity) LaunchBugReporter
0x00007FFB66FCAD0F (Unity) EditorMonoConsole::LogToConsoleImplementation
0x00007FFB66FCB80A (Unity) EditorMonoConsole::LogToConsoleImplementation
0x00007FFB67C7C3BD (Unity) DebugStringToFilePostprocessedStacktrace
0x00007FFB67C7B758 (Unity) DebugStringToFile