I have been studying a phenomenon with the villagers not going inside at night and I figured it out what's going on in creative mode the other day. It has to do with the beds that spawn in the village houses with the redesign to the village in newer updates.

In some villages, there are a lack of beds for villagers due to the redesign with the smaller houses only containing 1 bed each on average with 1or 2 bigger houses in bigger villages that contain more than one bed as shown in my pictures of the larger house containing 2 beds.

High populated villages will have villagers be stuck outside at night usually if there aren't enough beds in the houses for them to sleep in.

This issue affects any village in any biome that it spawns in so is not just limited to just one biome type.

I think a redesign for the 5x5 houses being turned into a 9x9 style would work nice but still keep things small and offer more room for beds.
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Edit: After this report was typed, some villagers will go into a nearby house at night with a bed for safety but not all of them. *
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