I’ve found the issue, which is related to not enabling early Z-pass (either None, or decide automatically). When I set it to Opaque Mesh for example, it works fine.
However, doing this does not work in VR, for some reason the left viewport then only shows lights, and particles systems, meshes are not visible anymore.
Basically, I’m trying to implement D-Buffer decal in VR. I got it working using this fix : DBuffer decals in Rift render in single eye - XR Development - Unreal Engine Forums
After this fix, I now see the decal correctly but the “bouncing and moving” behavior occurs.
Enabling early Z-pass fix the issue in normal mode, but in stereo : weird stuff.
Any idea where to look to fix this?