I've been trying to farm bees in my Survival world, but I have found that new bees I have created disappear after becoming adults. To test this further, I locked two Bees in an enclosure and breeded them, then kept checking on them and the baby. About 20 minutes later, when the bee would have grown up, I looked back in the cage and there were only 2 bees in there.

An alternate explanation is that the baby growing up is causing one of the parents to disappear, in which case this issue is likely a duplicate of MC-183139. However, I decided to post it separately in case my first theory was right and/or it was indeed a unique issue worth looking into. I apologize in advance if it wasn't.