Manually moved Particles with Streched Billboard mode

Hi,

I'm trying to manually move particles with the following code

Code (CSharp):

1.  
2. var particleCount = particleSystem.GetParticles(_ParticlesCache);
3. ParticleSystem.Particle particle;
4. for (var i = 0; i < particleCount; i++)
5. {
6.    particle = _ParticlesCache[i];
7.    particle.position += delta;
8.    _ParticlesCache[i] = particle;
9. }
10. particleSystem.SetParticles(_ParticlesCache, particleCount);
11.  

(delta vector is about 15 units long)

Everything works fine, the particles do change their location - but when particle Renderer Mode is set to Stretched Billboard there's a glitch (lasting one frame), where particles stretch A LOT in the direction of camera. They cover almost entire screen and it looks like a hyperdrive effect from the old sci-fi movies.
I suppose it is the effect of applying a large offset and some particle system internal velocity calculation - particles "travel" a large distance over one frame and are stretched accordingly.

I tried to store velocity of each particle before movement and and then set it afterwards (both velocity and animatedVelocity), but it didn't help.

Did anyone had similiar issue?