Reproduction steps:

1. Open the attached project.
2. Open the particles scene.
3. Select the Particle System in the hierarchy.
4. Observe the particle behavior(GIFs attached).
- Particles shakes/blinks all the time.
- When particle dies:
* Frame rate starts to decrease for disappearing particle trail.
* Trail starts to squash instead of continuously disappearing.

Reproduced with:
5.6.0a5

Regression introduced in:
Particle shake/blink - 5.6.0a2
Squashing 5.5.0a9

Note:
- If project crashes, delete Temp and Library folders before launch.
- Poke me if this bug should be split to 2-3.