To reproduce:

1. Download attached project "CamaroDemo17.zip" and open in Unity

Expected Result: In Console, no error occurs
Actual Result: In Console, error Assertion failed on expression: 'IsNormalized(normal' starts spamming

Note: Here's the callstack: https://gyazo.com/cdcf0ab1ecfcc6f68aa21dd376ae28df

It hits the assert here:

inline void Plane::Set3Points(const Vector3f& a, const Vector3f& b, const Vector3f& c)
{
normal = CalcRawNormalFromTriangle(a, b, c);
normal = ::Normalize(normal);
distance = -Dot(normal, a);
Assert(IsNormalized(normal));
}

normal = CalcRawNormalFromTriangle(a, b, c);` is returning a degenerate normal (0,0,0) because of two coincident points.
This is coming from the light shadow code.

Note: This issue appears both on Windows and OSX.

Reproduced on Unity 5.5.4p1, 5.6.2p1, 2017.1.0f1 and 2017.2.0b1