Steps to reproduce:

1. Download and import attached project. (ParticleAssert.zip)
2. Open Scene: "Particle Test Scene"
3. Select any particle system from "Container" game object in Hierarchy
4. Leave particles looping for 30-60 secs
5. Check console:

Assert shows up in console:

inIndex == 0 || (inValue >= 0.0f) == (sort[0].floatValue >= 0.0f)

Reproduced on: 5.4.0f3, 5.3.6p3
Not reproduced: 5.5.0a6