I want to replace Quark's Vertical Slabs with this mod but when tying out this mod I easily found a bug that involves creating an infinite water source within a small wall made up of four horizontal stairs. When it creates a water source, for whatever reason it auto-updates the stairs the wrong way:

I also did this with slabs, and it does the same thing here:

I want to see if you can fix this bug so that I may use this mod. Cause otherwise I may have to go back to enabling Quark's vertical slabs.

You completely failed to mention if this is forge or fabric. I tested both and couldn't reproduce the issue. It's probably either another mod messing with how waterlogging works in some weird way that causes the blocks to revert to their "base" states, or I've actually fixed this without realizing it.