nParticles collisions issue


Hi guys I really hope someone can help me resolve this issue.
Essentially I have an nParticle instanced shape set up of which falls and collides with geo.
I didnt though need the nParticles to stay on the collision surface so have them at creation with a long LifespanPP, then a runtime expression that changes the lifespanPP to be much shorted once the velocity of the particle goes below a certain value.
All worked fine …but as soon as I animate the emission values on playback loop, on second or third (no particular order) playback starts to stutter, and freeze and worse crashes Maya.
As soon as I delete the nRigid it plays back fine again.
So I recreated and tried to not have the expression looking at velocity and still it eventually does the same.
I even just did a standard collision event vis the menu to kill particle on collision and again it starts to mess up.
Whatever I do it seems to eventually have issues.
I have even tried on co-workers machines and still does the same to the point all of us are dumbfounded and a
I even tried on both Maya 2016/2017/ and 2018 and still does the same.
SaltFall_collisons_bug.mb (615.5 KB)