Stephen Howard

I believe im facing the same issue. Here's my reddit thread i made with a video and gifs of the issue. Essentially blocks originating from specifically only two of the four cardinal directions are creating a '9th block'.  https://www.reddit.com/r/Minecraft/comments/r1wvvv/help_why_does_my_water_when_placed_from/

Edit: i was able to attach one of the gifs directly here but the others were too large.