Crazy glitch with dual camera setup

Hi,

I encountered a weird bug where my particle systems sometimes render in a weird way. Here is how it looks:

https://imgur.com/n44wZUl

Background: I am working on a VR game for the Vive, and I have a two-camera setup in the scene, one has near plane and far plane quite small (0.1 - 60), clear depth only, and the other is (59-3000) and clear skybox. I have this setup because I am trying to avoid Z-fighting for a very large scene in which I have a procedural mesh (ski slope - red green black texture in the gif) and trampolines/ramps that are placed quite tangential to the slope (cannot see in gif). The particle texture is a white circle, similar to what seems to be the tiled texture in the glitches. On deactivating/reactivating the particle systems, it is obvious they are part of the problem.

I am sure the dual camera setup is also part of the problem because if I disable either the near or far camera, the other does not show any trace of the glitch. I would be happy to get rid of this setup, if there was some way to avoid Z-fighting.

The question is: how do I avoid both this glitch AND z-fighting, keeping the maximum visible distance to around 3000?

PS: please tell me where I should move this thread if this is not the right place for it. Thanks!