Villagers are not successfully breeding

When providing villagers with enough food, beds and workstations (not sure if all of them are required), they show the breeding hearts, but the process never finishes: Instead, they stand still for minutes until they get distracted by work tasks or the setting sun.

To reproduce, just fence in two villagers with a house with a few beds nearby, build some workstations and throw bread at them. Usually they start within a few moments if you execute /time set day.