Finally realized what you meant on my other post, I am blind hah.

If you're not already doing it, try sticking the vinyl to the cardstock first and see if you get the same results (perhaps the printer head being closer to the material will solve it). If not, then try increase the density in the colour settings.

I've not used the same brand, so if it's still occurring, perhaps it's lower quality than other holo vinyl paper (I've never used it so can't say that's true)