When bees are locked in a room near beehives, they can still enter hives fully covered by blocks. This does not happen in open areas as they only have a small chance to enter the hive. Makes it hard to breed bees without them returning to their hives.

In the attached screenshot, the bees fill both the hive and nest in less than 30s. They cannot enter if the there are 2 blocks surrounding the hive on all sides, but if there are less than 2 on any side, bees may enter through that side.