At the gaps in the base of the pedestal, the top face of the astral pillar (one tile high varient) becomes invisible.

@P3pp3rF1y I reported this as an issue in Astral's github and they bounced me right back here saying:

Their Bounding box is set up that it's filling the entire 12x12 box on the bottom, thus minecraft's rendering presumes that the entire area is filled with a solid model, as Reliquary's passive pedestal block is set up to count as a solid.
That's not my issue and nothing i can do about it from my end as it's their block's properties.

You will need to report this to astral as that is an issue with their block not rendering whent there's a non full block above it.