I'm building a villager farm, and I noticed that the villagers were walking a little strangly. After some examination, I realized they were avoiding the obsidian in the floor and walking on the cobblestone instead, unless their path requires them to walk over obsidian. The floor of this building is also the roof of a gold farm involving zombie pigmen, so the obsidian is all part of several nether portals. The world I'm on is on a bedrock dedicated server, in case that's important to know.