SubUV Movie flickering when the particle is scaled

Hi, guys! First of all sorry if this is not the right category, not sure where to put it.

I have this very simple particle effect on a game I’m working on that’s displaying just fine when the scale is the default (1.0 in the world object, and 3000 for XYZ in the Initial Size module of the particle). But when the particle is scaled, for example, to 4 or 5 in the world (or 12000 in the Initial Size module), it gets a flickering thing, like this on this GIF.

Does anyone know the cause and how to fix this? First time happening here and I’m not really a VFX artist, so any help appreciated!

EDIT: Discovered it’s the Particle Cutout effect giving this artifact. Any way to minimize it?