When leashed, and then unleashed, tames (bears, gorillas, elephants etc.) are bugged and don't want to attack mobs that players hit/are attacked by. When leashed again, they work normally, but after another unleashing they are bugged again.

This is still a bug in the latest release. I initially thought that this was due to me using a Bow, Trident, or any other projectile weapon while riding an Elephant and that my Elephant could not see me attacking it. I got attacked by a Grizzly Bear with my Elephant right next to me, and my Elephant did not care. Although, I have seen my Elephant fight back when attacked by another mob. I had no idea that this affected Grizzly Bears, Gorillas, and other tamable mobs.