I have previously had issues (very occasionally) with villagers despawning in enclosed protected environmentrs (within automatic wheat, carrot and potato farms) and disappearing hopper minecarts. However, I just had an issue where all villagers, minecarts and item frames within a row of chunks all disappeared. This row of chunks bisected my villager trading hall and my storage room. This is not the visual glitch mentioned elsewhere - relogging did not bring them back. They are gone. All item frames, minecarts and villagers in immediately adjacent chunks persist as expected. The configuration of affected chunks (a single row of chunks - at least 4 chunks long) makes me think the issue occurred when these chunks were loaded, as this would have happened simultaneously.