Hey everyone out there.
I created a particle tornado and every particle has an object copied on it with a copy node.
To have different objects copied/instanced, I used a switch node to let them randomly appear on the points. Each point displays one of the objects from within the switch node. It's a very simple setup.
Everything works fine until frame 133, where the instanced objects on each particle changes to other objects from the pool of the switch node randomly after a few frames. If you don't know what I mean, just have a look at the hip file and scrub threw the timeline beyond 133 frames. I also attached the Obj with the different objects in it.

I hope someone can help me. I'm still very new to houdini, so it could be a stupid beginners mistake.

I'm not 100% sure what is wrong with your setup, but I replaced 6 objects in your file node with simple objects with varying scales, and I changed our rand switch function to operate with fit01(rand(@id), 0, 5) instead of @ptnum, because your @ptnum is changing, which created the difference in copy stamps frame by frame. Using @id fixes that, but it didn't with your file node. When I changed the geometry that was being copied, the issue went away, which leads me to believe something is happening with the way your file node was written out.

Hey Midasssilver, thanks for your response.

Alternatively I could instead of killing the particles (that's the reason why they start jumping I figured out meanwhile xD) at the end, just make them invisible, but I don't know how to achieve this, to make those objects/points invisible after passing a specific area in space. Any idea? I'll replace the geometry anyway later, but to be sure it'll work, I'd prefer to make them just invisible.

I have kind of the same issue in a flip fluid simulation, where I replaced some particles with spheres to create bubbles. I watched that great tutorial form BW Design (https://vimeo.com/153856342 [vimeo.com]) and basically rebuilt it.

After a fiew frames, the bubbles starts jumping around wildly. I guess some particles gets killed, probably because of some colliders. It happens even if Age Particles and Reap Particles is unckecked in the flip solver. Do you think this problems have something to do with each other?

Well u can reduce the pscale of particles below a certain Y value to 0,which would make them disappear. You can also ramp down that value so it is more gradual if you want. But yes, changing point count will change your copy result, if you use @ptnum, that's why I'd suggest using id

I didn't know how to do this with the Y value but I just used the hitnum to scale it to zero and placed the collider where they have to die off. to use id is for sure better at all. Thanks for your responses, they helped me a lot.

The other problem, I will try to figure out the issue first by myselve. Otherwise I would create a new topic. It seems to be a different kind of dilemma.