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[SOLUTION] Unreal Editor Crash with Assertion failed Missing required implementation

With Unreal Engine 4.27.2 the crash error message:

Assertion failed: 0 && “Missing required implementation.” [File:D:\Build++UE4\Sync\Engine\Source\Runtime\AIModule\Classes\Navigation/CrowdAgentInterface.h] [Line: 19]

This was a random crash on play in editor - caused by enabling “Initially loaded” and or “Initially visible” on a streaming level.
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This crash may be due to an AI actor present in the level who was still loading while the level state was loaded.