The bug

Leading a bee to their nest/hive, it will normally drop the lead once it enters to do its work. Although if you stand a few distance away and the bee leaves its nest/hive, the lead gets duplicated. The game may think that the bee is still attached to the lead even when it enters the nest/hive

To reproduce

1. Lead a bee to their nest/hive
2. Watch it drop the lead once it enters the nest/hive
3. Let it do its work, but stand a few distance away, like 20 blocks
4. Once it leaves the nest/hive, go back to it
    The lead gets duplicated

Screenshots below for reproducion: