Can't place any block in random areas of this 19w02a server/survival. Pathways in this village were undergoing construction and some blocks cannot be replaced. We made sure there were no invisible villagers. We can make a tower and drop sand on it, but directly placing a block makes it appear for a flash and disappear, reappearing in the inventory only if you click where you had it, or place another block somewhere.

Edit: Like I said, there were no villagers because we could use a tower to drop sand on the area and the villager would've suffocated. I also said I went into survival/single player mode and so villagers were absolutely not gonna get in the way of it. This was happening outside the village, in mines, and so forth.