Short description of error
When animating the particle seed value for hair system, you don't get different locations for each particle. The particles are always in the same place, but you get random particle object if you are using particle objects.
If you manually change the seed value it works as it should work.
Exact steps for others to reproduce the error
Create particle system with hair particles. Change the seed value. See the effect. Now add keyframes to the seed value. It's not working as it should.